The Lancet Infectious Diseases

BackgroundThe ongoing outbreak of SARS-CoV-2 Omicron BA.2 infections in Hong Kong, the model city of universal masking of the world, has resulted in a major public health crisis. Although the third vaccination resulted in strong boosting of neutralization antibody, vaccine efficacy and corelates of immune protection against the major circulating Omicron BA.2 remains to be investigated. MethodsWe investigated the vaccine efficacy against the Omicron BA.2 breakthrough infection among 470 public servants who had received different SARS-CoV-2 vaccine regimens including two-dose BNT162b2 (2xBNT, n=169), three-dose BNT162b2 (3xBNT, n=170), two-dose CoronaVac (2xCorV, n=34), three-dose CoronaVac (3xCorV, n=67) and third-dose BNT162b2 following 2xCorV (2xCorV+1BNT, n=32). Humoral and cellular immune responses after three-dose vaccination were further characterized and correlated with clinical characteristics of BA.2 infection. FindingsDuring the BA.2 outbreak, 27.7% vaccinees were infected. The timely third-dose vaccination provided significant protection with lower incidence rates of breakthrough infections (2xBNT 49.2% vs 3xBNT 13.1%, p <0.0001; 2xCorV 44.1% vs 3xCoV 19.4%, p=0.003). Investigation of immune response on blood samples derived from 92 subjects in three-dose vaccination cohorts collected before the BA.2 outbreak revealed that the third-dose vaccination activated spike (S)-specific memory B cells and Omicron cross-reactive T cell responses, which correlated with reduced frequencies of breakthrough infections and disease severity rather than with types of vaccines. Moreover, the frequency of S-specific activated memory B cells was significantly lower in infected vaccinees than uninfected vaccinees before vaccine-breakthrough infection whereas IFN-{gamma}+ CD4 T cells were negatively associated with age and viral clearance time. Critically, BA.2 breakthrough infection boosted cross-reactive memory B cells with enhanced cross-neutralizing antibodies to Omicron sublineages, including BA.2.12.1 and BA.4/5, in all vaccinees tested. InterpretationOur results imply that the timely third vaccination and immune responses are likely required for vaccine-mediated protection against Omicron BA.2 pandemic. Although BA.2 conferred the highest neutralization resistance compared with variants of concern tested before the emergence of BA.2.12.1 and BA.4/5, the third dose vaccination-activated S-specific memory B cells and Omicron cross-reactive T cell responses contributed to reduced frequencies of breakthrough infection and disease severity. Neutralizing antibody potency enhanced by BA. 2 breakthrough infection with previous 3 doses of vaccines (CoronaVac or BNT162b2) may reduce the risk for infection of ongoing BA.2.12.1 and BA.4/5. FundingHong Kong Research Grants Council Collaborative Research Fund, Health and Medical Research Fund, Wellcome Trust, Shenzhen Science and Technology Program, the Health@InnoHK, Innovation and Technology Commission of Hong Kong, China, National Program on Key Research Project, Emergency Key Program of Guangzhou Laboratory, donations from the Friends of Hope Education Fund and the Hong Kong Theme-Based Research Scheme.

ImportanceThe SARS-CoV-2 non-spike structural proteins of nucleocapsid (N), membrane (M) and envelope (E) are critical in the host cell interferon response and memory T-cell immunity and have been grossly overlooked in the development of COVID vaccines. ObjectiveTo determine the safety and immunogenicity of UB-612, a multitope vaccine containing S1-RBD-sFc protein and rationally-designed promiscuous peptides representing sequence-conserved Th and CTL epitopes on the Sarbecovirus nucleocapsid (N), membrane (M) and spike (S2) proteins. Design, setting and participantsUB-612 booster vaccination was conducted in Taiwan. A UB-612 booster dose was administered 6-8 months post-2nd dose in 1,478 vaccinees from 3,844 healthy participants (aged 18-85 years) who completed a prior placebo (saline)-controlled, randomized, observer-blind, multi-center Phase-2 primary 2-dose series (100-g per dose; 28-day apart) of UB-612. The interim safety and immunogenicity were evaluated until 14 days post-booster. ExposureVaccination with a booster 3rd-dose (100-g) of UB-612 vaccine. Main outcomes and measuresSolicited local and systemic AEs were recorded for seven days in the e-diaries of study participants, while skin allergic reactions were recorded for fourteen days. The primary immunogenicity endpoints included viral-neutralizing antibodies against live SARS-CoV-2 wild-type (WT, Wuhan strain) and live Delta variant (VNT50), and against pseudovirus WT and Omicron variant (pVNT50). The secondary immunogenicity endpoints included anti-S1-RBD IgG antibody, S1-RBD:ACE2 binding inhibition, and T-cell responses by ELISpot and Intracellular Staining. ResultsNo post-booster vaccine-related serious adverse events were recorded. The most common solicited adverse events were injection site pain and fatigue, mostly mild and transient. The UB-612 booster prompted a striking upsurge of neutralizing antibodies against live WT Wuhan strain (VNT50, 1,711) associated with unusually high cross-neutralization against Delta variant (VNT50, 1,282); and similarly with a strong effect against pseudovirus WT (pVNT50, 6,245) and Omicron variant (pVNT50, 1,196). Upon boosting, the lower VNT50 and pVNT50 titers of the elderly in the primary series were uplifted to the same levels as those of the young adults. The UB-612 also induced robust, durable VoC antigen-specific Th1-oriented (IFN-{gamma}+-) responses along with CD8+ T-cell (CD107a+-Granzyme B+) cytotoxicity. Conclusions and relevanceWith a pronounced cross-reactive booster effect on B- and T-cell immunity, UB-612 may serve as a universal vaccine booster for comprehensive immunity enhancement against emergent VoCs. Trial registration[ClinicalTrials.gov: NCT04773067] KEY POINTSO_ST_ABSQuestionC_ST_ABSFacing ever-emergent SARS-CoV-2 variants and long-haul COVID, can composition-updated new vaccines be constructed capable of inducing striking, durable booster-recalled B/T-immunity to prevent infection by VoCs? FindingsIn a Phase-2 extension study, a booster dose of UB-612 multitope protein-peptide vaccine prompted high viral-neutralizing titers against live wild-type virus (VNT50, 1,711), Delta variant (VNT50, 1,282); pseudovirus wild-type (pVNT50, 6,245) and Omicron variant (pVNT50, 1,196). Robust, durable Th1-IFN{gamma}+ responses and CD8+ T cell-(CD107a+-Granzyme B+) cytotoxic activity were both observed. MeaningUB-612 RBD-sFc vaccine armed with T cell immunity-promoting conserved N, M and S2 Th/CTL epitope peptides may serve as a universal vaccine to fend off new VoCs.

BackgroundMost of current approved vaccines, based on a Spike-only as single immunogen, fall short of producing a full-blown T-cell immunity. SARS-CoV-2 continues to evolve with ever-emergent higher-contagious mutants that may take a turn going beyond Omicron to bring about a new pandemic outbreak. New recombinant SARS-CoV-2 species could be man-made through genetic manipulation to infect systemically. Development of composition-innovated, pan-variant COVID-19 vaccines to prevent from hospitalization and severe disease, and to forestall the next pandemic catastrophe, is an urgent global objective. Methods and findingsIn a retrospective, e-questionnaire Observational Study, extended from a clinical Phase-2 trial conducted in Taiwan, during the prime time of Omicron outbreak dominated by BA.2 and BA.5 variants, we investigated the preventive effects against COVID-19 moderate-severe disease (hospitalization and ICU admission) by a pan-Sarbecovirus vaccine UB-612 that targets monomeric S1-RBD-focused subunit protein and five designer peptides comprising sequence-conserved, non-mutable helper and cytotoxic T lymphocyte (Th/CTL) epitopes derived from Spike (S2), Membrane (M) and Nucleocapsid (N) proteins. Per UB-612 vaccination, there were no hospitalization and ICU admission cases (0% rate, 6 months after Omicron outbreak) reported [&ge;]14 months post-2nd dose of primary series, and [&ge;]10 months post-booster (3rd dose), to which the potent memory cytotoxic CD8 T cell immunity may be the pivotal in control of the infection disease severity. Six months post-booster, the infection rate (asymptomatic and symptomatic mild) was only 1.2%, which increased to 27.8% observed [&ge;]10 months post-booster. The notable protection effects are in good alignment with a preliminary Phase-3 heterologous booster trial report showing that UB-612 can serve as a competent booster substitute for other EUA-approved vaccine platforms to enhance their seroconversion rate and viral-neutralizing titer against Omicron BA.5. ConclusionsUB-612, a universal multitope vaccine promoting full-blown T cell immunity, may work as a competent primer and booster for persons vulnerable to Sarbecovirus infection. Trial RegistrationClinicalTrials.gov ID: NCT04773067. AUTHOR SUMMARYA COVID-19 vaccine based on a Spike-only single immunogen would fall short of producing a full-blown, escape-proof T cell immunity. In Omicron era plagued with ever-evolving and higher-contagious SARS-CoV-2 mutants, immune antibodies against variants beyond BA.5 are seen on a cliff drop, rendering the viral-neutralizing titer strength an increasingly less relevant immunity parameter. The true, urgent issue at heart in vaccine development has not been updating variant component to increase antibody titer for prevention of infection, but to validate universal vaccines that would have a potential to head off hospitalization, severe disease and ultimately reinfection altogether, and so to forestall a new catastrophe of pandemic outbreak. To reach the ideal goals, a universal vaccine able to produce potent, broadly recognizing and durable memory T cell immunity would be essential. UB-612, a pan-Sarbecovirus T cell immunity-promoting mutitope vaccine, has been shown to provide strong and long-lasting [&ge;]10 month protective effect against COVID-19 moderate-severe disease (0% cases of hospitalization and ICU admission). UB-612 is a unique S1-RBD subunit protein vaccine armed with five designer peptides comprising sequence-conserved helper and cytotoxic T lymphocyte (Th/CTL) epitopes derived from Spike (S2x3), Membrane (M) and Nucleocapsid (N) proteins across Sarbecovirus species.

To inform vaccine development strategies, we aimed to systematically review evidence on the prevalence and distribution of non-typhoidal Salmonella enterica serogroups and serovars. We searched four databases from inception through 4 June 2021. We included articles that reported at least one non-typhoidal Salmonella enterica strain by serogroup or serovar isolated from a normally sterile site. Of serogrouped isolates, we pooled the prevalence of serogroup O:4, serogroup O:9, and other serogroups using random-effects meta-analyses. Of serotyped isolates, we pooled the prevalence of Salmonella Typhimurium (member of serogroup O:4), Salmonella Enteritidis (member of serogroup O:9), and other serovars. Of 82 studies yielding 24,258 serogrouped isolates, pooled prevalence (95% CI) was 44.7% (36.3%-48.3%) for serogroup O:4, 45.4% (36.9%-49.0%) for serogroup O:9, and 9.9% (6.1%-13.3%) for other serogroups. Pooled prevalence (95%CI) was 36.8% (29.9%-44.0%) for Salmonella Typhimurium, 37.8% (33.2%-42.4%) for Salmonella Enteritidis, and 18.4% (11.4%-22.9%) for other serovars. Of global serogrouped non-typhoidal Salmonella isolates from normally sterile sites, serogroup O:4 and O:9 together accounted for 90%. Of global serotyped isolates, serovars Typhimurium and Enteritidis together accounted for 75%. Vaccine development strategies covering serogroups O:4 and O:9, or serovars Typhimurium and Enteritidis, have the potential to prevent the majority of non-typhoidal Salmonella invasive disease. PROSPERO:CRD42022376658. Key resultsO_LIInvasive infections in normally sterile sites caused by non-typhoidal Salmonella have a case fatality ratio of 15%. C_LIO_LIVaccine products for human non-typhoidal Salmonella are in currently in development. C_LIO_LIFor future vaccine strategies, we provide global non-typhoidal Salmonella serogroup and serovar coverage by region and by age groups. C_LIO_LISerogroups O:4 and O:9 account for 90% of isolates of non-typhoidal Salmonella enterica from normally sterile sites. C_LIO_LISerovars Typhimurium and Enteritidis, members of serogroup O:4 and O:9, respectively, cover 75% of isolates of non-typhoidal Salmonella enterica from normally sterile sites. C_LI

BackgroundLongitudinal data are lacking to compare booster effects of Delta breakthrough infection versus the third vaccine dose on neutralizing antibodies (NAb) against Omicron. MethodsParticipants were the staff of a national research and medical institution in Tokyo who attended serological surveys on June 2021 (baseline) and December 2021 (follow-up); in between, the Delta-dominant epidemic occurred. Of 844 participants who were infection-naive and had received two doses of BNT162b2 at baseline, we identified 11 breakthrough infections during the follow-up. One control matched to each case was randomly selected from those who completed the booster vaccine and those who were unboosted by the follow-up. We used the generalized estimating equation model to compare live-virus NAb against Wuhan, Delta, and Omicron across groups. ResultsPersons who experienced breakthrough infection showed marked increases in NAb titers against Wuhan (4.1-fold) and Delta (5.5-fold), and 64% had detectable NAb against Omicron at follow-up, although the NAb against Omicron after breakthrough infection was 6.7- and 5.2-fold lower than that against Wuhan and Delta, respectively. The increase was apparent only in symptomatic cases and as high as in the third vaccine recipients. In contrast, these titers largely decreased (Wuhan, Delta) or remained undetected (Omicron) at follow-up in infection-naive and unboosted persons. ConclusionsSymptomatic breakthrough infection during the Delta predominant wave was associated with significant increases in NAb against Wuhan, Delta, and Omicron, similar to the third BNT162b2 vaccine. Given the much lower cross-NAb against Omicron than other virus types, however, infection prevention measures must be continued irrespective of vaccine and infection history while the immune evasive variants are circulating. Key pointsSymptomatic, not asymptomatic, SARS-CoV-2 breakthrough infection after the second BNT162b2 vaccination during the Delta-predominant wave enhanced neutralizing antibodies against Wuhan, Delta, and Omicron comparable to the three vaccine doses, although immunity against Omicron was much lower than Wuhan and Delta.

BackgroundLicensed mRNA vaccines demonstrated initial effectiveness against COVID-19 but require booster doses to broaden the anti-SARS-CoV-2 response. There is an unmet need for novel highly immunogenic and broadly protective vaccines. We compared immunogenicity and tolerability of ARCT-154, a novel self-amplifying mRNA vaccine with the mRNA vaccine, Comirnaty(R). MethodsWe compared immune responses to ARCT-154 and Comirnaty booster doses in healthy 18- 77-year-old Japanese adults initially immunised with two doses of mRNA COVID-19 vaccine (Comirnaty or Spikevax(R)) then a third dose of Comirnaty at least 3 months previously. Neutralising antibodies were measured before and 28 days after booster vaccination. The primary objective was to demonstrate non-inferiority of the immune response against Wuhan-Hu-1 SARS-CoV-2 virus as geometric mean titre (GMT) ratios and seroresponse rates (SRR) of neutralising antibodies; key secondary endpoints included the immune response against the Omicron BA.4/5 variant and vaccine tolerability assessed using participant-completed electronic diaries. FindingsBetween December 13, 2022 and February 25, 2023 we enrolled 828 participants randomised 1:1 to receive ARCT-154 (n = 420) or Comirnaty (n = 408) booster doses. Four weeks after boosting, ARCT-154 induced higher Wuhan-Hu-1 neutralising antibodies GMTs than Comirnaty (5641 [95% CI: 4321, 7363] and 3934 [2993, 5169], respectively), a GMT ratio of 1{middle dot}43 (95% CI: 1{middle dot}26-1{middle dot}63), with SRR of 65{middle dot}2% (60{middle dot}2-69{middle dot}9) and 51{middle dot}6% (46{middle dot}4-56{middle dot}8) meeting the non-inferiority criteria. Respective anti-Omicron BA.4/5 GMTs were 2551 (1687-3859) and 1958 (1281-2993), a GMT ratio of 1{middle dot}30 (95% CI: 1{middle dot}07-1{middle dot}58), with SRR of 69{middle dot}9% (65{middle dot}0-74{middle dot}4) and 58{middle dot}0% (52{middle dot}8-63{middle dot}1), meeting the superiority criteria for ARCT-154 over Comirnaty. Booster doses of either ARCT-154 or Comirnaty were equally well-tolerated with no causally-associated severe or serious adverse events; 94{middle dot}8% and 96{middle dot}8% of ARCT-154 and Comirnaty vaccinees reported local reactions and 65{middle dot}7% and 62{middle dot}5% had solicited systemic adverse events. Events were mainly mild in severity, occurring and resolving within 3-4 days of vaccination. InterpretationImmune responses four weeks after an ARCT-154 booster dose in mRNA-immunised adults were higher than after a Comirnaty booster, meeting non-inferiority criteria against the prototype Wuhan-Hu-1 virus, and superiority criteria against the Omicron BA.4/5 variant. FundingThe study was funded by the Japanese Ministry of Health, Labour, and Welfare following a public invitation to bid for an urgent improvement project for vaccine manufacturing systems, fourth invitation, Grant number: 1212-3. Clinical Trials registration and identifierThe study was registered on the Japan Registry for Clinical Trials (jRCT 2071220080).

BackgroundIntroducing the pneumococcal conjugate vaccines (PCV) into the routine childhood immunisation schedule in England has reduced pneumococcal disease burden. Nonetheless, pneumococcal disease continues to a]lict marked morbidity and mortality in the population, including young children. In January 2020, England transitioned from a "2+1" PCV schedule (two primary doses at 8 and 16 weeks, with a booster dose at 12 months) to a "1+1" PCV schedule (single primary dose at 12 weeks and a booster dose at 12 months). While immunogenicity studies suggested comparable protection, reducing primary vaccine doses places greater emphasis on timely booster uptake. MethodsWe examine national trends in PCV uptake before and after the schedule change and quantify inequalities by deprivation. We analysed quarterly vaccine uptake data for 2013-2025 from the Cover of Vaccination Evaluated Rapidly (COVER) programme for upper-tier local authorities in England linked to 2019 Index of Multiple Deprivation quintiles. We examined booster gaps - the di]erence between primary coverage at 12 months and booster coverage at 24 months. We estimated susceptibility to pneumococcal disease (by birth cohort stratified by quarter) by combining observed PCV uptake with published vaccine e]ectiveness estimates. FindingsBooster retention deteriorated following the schedule change; mean booster gaps increased from 2.32% (2+1 period) to 4.79% (1+1 period). The largest booster gaps arose in London boroughs. The gap between least and most deprived quintiles widened from 2-3% (2+1 period) to 4-6% (1+1 period). Susceptibility calculations returned notable geographical variation in estimated vaccine type invasive pneumococcal disease susceptibility in England, with disproportionate burden in deprived areas. InterpretationsThe success of the 1+1 schedule depends on maintaining equitable, high booster uptake. Declining booster retention and widening inequalities threaten programme e]ectiveness. Increased resource allocation for child immunisations, strengthened follow-up systems and targeted interventions in deprived communities are essential to prevent widening protection gaps. FundingNo specific funding for this project. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSPneumococcal conjugate vaccines (PCVs) have been part of the routine childhood immunisation schedule in England since September 2006, firstly using PCV7 (targeting seven serotypes) and then from 2010 PCV13 (targeting thirteen serotypes). This has resulted in reduced invasive pneumococcal disease (IPD) burden, although IPD continues to cause marked morbidity and mortality across the population, including young children. Originally administered as a "2+1" schedule (two primary doses at 8 and 16 weeks, with a booster dose at 12 months), England transitioned In January 2020 to a "1+1" PCV schedule (single primary dose at 12 weeks and a booster dose at 12 months). While immunogenicity studies suggested comparable protection, reducing primary vaccine doses places greater emphasis on timely booster uptake. We searched PubMed, Google Scholar, and medRxiv for articles published in English from inception to 30 Nov 2025 with the following search terms: ("PCV-13" OR "13-valent pneumococcal conjugate vaccine" OR "pneumococcal conjugate vaccine") AND (booster OR "third dose" OR "2+1 schedule" OR "additional dose") AND (children OR infants OR toddlers OR paediatric OR paediatric) AND ("vaccine e]ectiveness" OR "vaccine e]icacy") AND "England". To our knowledge, an observational analysis investigating potential inequalities in Childhood Pneumococcal Conjugate Vaccine Uptake and resultant susceptibility to IPD in England Before and After the change from a 2+1 to 1+1 schedule in January 2020 has not been conducted. Added value of this studyWe analysed temporal and spatial trends and inequalities in PCV13 uptake across England at an Upper Tier Local Authority level for 2013-2025. This period included the January 2020 transition from a 2+1 to 1+1 dose schedule. The analysis revealed three critical findings: booster retention deteriorated under the 1+1 schedule; socioeconomic inequalities in vaccine uptake persisted and widened (particularly a]ecting the most deprived communities); using a susceptibility calculation that combined PCV uptake data with current knowledge on vaccine e]ectiveness estimates for PCV13 against vaccine type IPD, we highlight a growing inequitable susceptibility to vaccine type IPD in child cohorts. Implications of all the available evidenceOur study shows that PCV booster retention has notably declined in England since the change from a 2+1 to a 1+1 schedule change. This means the full protective potential of the 1+1 schedule is not being realised. A trend of lower booster retention amongst children in more deprived areas risks avoidable disease burden being concentrated in the most disadvantaged communities and widening health inequalities. Other countries considering a 1+1 schedule change should consider underlying inequality in vaccine uptake and booster retention before implementation. Systems strengthening and targeted, equity-focused interventions are needed to address the identified coverage gaps.

BackgroundThe announcement of efficacious vaccine candidates against SARS-CoV-2 has been met with worldwide acclaim and relief. Many countries already have detailed plans for vaccine targeting based on minimising severe illness, death and healthcare burdens. Normally, relatively simple relationships between epidemiological parameters, vaccine efficacy and vaccine uptake predict the success of any immunisation programme. However, the dynamics of vaccination against SARS-CoV-2 is made more complex by age-dependent factors, changing levels of infection and the potential relaxation of non-pharmaceutical interventions (NPIs) as the perceived risk declines. MethodsIn this study we use an age-structured mathematical model, matched to a range of epidemiological data in the UK, that also captures the roll-out of a two-dose vaccination programme targeted at specific age groups. FindingsWe consider the interaction between the UK vaccination programme and future relaxation (or removal) of NPIs. Our predictions highlight the population-level risks of early relaxation leading to a pronounced wave of infection, hospital admissions and deaths. Only vaccines that offer high infection-blocking efficacy with high uptake in the general population allow relaxation of NPIs without a huge surge in deaths. InterpretationWhile the novel vaccines against SARS-CoV-2 offer a potential exit strategy for this outbreak, this is highly contingent on the infection-blocking (or transmission-blocking) action of the vaccine and the population uptake, both of which need to be carefully monitored as vaccine programmes are rolled out in the UK and other countries. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSVaccination has been seen as a key tool in the fight against SARS-CoV-2. The vaccines already developed represent a major technological achievement and have been shown to generate significant immune responses, as well as offering considerable protection against disease. However, to date there is limited information on the degree of infection-blocking these vaccines are likely to induce. Mathematical models have already successfully been used to consider age- and risk-structured targeting of vaccination, highlighting the importance of prioritising older and high-risk individuals. Added value of this studyTranslating current knowledge and uncertainty of vaccine behaviour into meaningful public health messages requires models that fully capture the within-country epidemiology as well as the complex roll-out of a two-dose vaccination programme. We show that under reasonable assumptions for vaccine efficacy and uptake the UK is unlikely to reach herd immunity, which means that non-pharmaceutical interventions cannot be released without generating substantial waves of infection. Implications of all the available evidenceVaccination is likely to provide substantial individual protection to those receiving two doses, but the degree of protection to the wider population is still uncertain. While substantial immunisation of the most vulnerable groups will allow for some relaxation of controls, this must be done gradually to prevent large scale public health consequences.

We estimated XBB.1.5 vaccine effectiveness against hospitalization/death among adults aged [&ge;]50 years. Compared with non-XBB.1.5 vaccinees, the initial protection of 64% (95%CI, 57%-69%) was reduced when JN/KP-sublineages became predominant, and quickly declined. No significant protection was observed >6 months post-vaccination. Short durability of protection poses unique challenges for COVID-19 vaccination.

BackgroundDespite the availability of effective vaccines against coronavirus disease 2019 (Covid-19), the emergence of variant strains and breakthrough infections pose a challenging new reality. Booster vaccinations are needed to maintain vaccine-induced protection. MethodsENSEMBLE2 is an ongoing, randomized, double-blind, placebo-controlled, phase 3 pivotal trial including crossover vaccination after emergency authorization of Covid-19 vaccines. Adults aged [&ge;]18 years were randomized to receive Ad26.COV2.S or placebo as a primary dose plus a booster dose at two months. The primary endpoint was vaccine efficacy against the first occurrence of molecularly-confirmed moderate to severe-critical Covid-19 with onset [&ge;]14 days after booster vaccination in the per-protocol population. Key efficacy, safety, and immunogenicity endpoints were also assessed. ResultsThe double-blind phase enrolled 31,300 participants, 14,492 of whom received 2 doses and were evaluable for efficacy (per-protocol set, Ad26.COV2.S n=7484; placebo n=7008). Baseline demographics and characteristics were balanced. Vaccine efficacy was 75.2% (adjusted 95% CI, 54.6-87.3) against moderate to severe-critical Covid-19 and was similar against symptomatic infection (75.6% [55.5-99.9]). Efficacy was consistent across participants with and without comorbidities, and reached 93.7% (58.5-99.9) in the US. Vaccine efficacy against severe-critical Covid-19 was 100% (32.6-100.0; 0 vs 8 cases). The booster vaccine induced robust humoral responses and exhibited an acceptable safety profile. ConclusionsA homologous Ad26.COV2.S booster administered 2 months after primary single-dose vaccination in adults led to high vaccine efficacy, including against any symptomatic infection and SARS-CoV-2 variants prevalent during the study. (Funding: Janssen Research and Development and others; ENSEMBLE2 ClinicalTrials.gov number, NCT04614948.)

BackgroundThe rapid worldwide spread of the mildly pathogenic SARS-CoV-2 Omicron variant has led to the suggestion that it will induce levels of collective immunity that will help putting an end to the COVID19 pandemics. MethodsConvalescent serums from non-hospitalized individuals previously infected with Alpha, Delta or Omicron BA.1 SARS-CoV-2 or subjected to a full mRNA vaccine regimen were evaluated for their ability to neutralize a broad panel of SARS-CoV-2 variants. FindingsPrior vaccination or infection with the Alpha or to a lesser extent Delta strains conferred robust neutralizing titers against most variants, albeit more weakly against Beta and even more Omicron. In contrast, Omicron convalescent serums only displayed low level of neutralization activity against the cognate virus and were unable to neutralize other SARS-CoV-2 variants. InterpretationModerately symptomatic Omicron infection is only poorly immunogenic and does not represent a substitute for vaccination. FundingEPFL COVID Fund; private foundation advised by CARIGEST SA; Private Foundation of the Geneva University Hospitals; General Directorate of Health of the canton of Geneva, the Swiss Federal Office of Public Health.

BackgroundReducing the risks of vaccine-derived polioviruses and vaccine-associated paralytic poliomyelitis from type 1 or 3 Sabin-strain oral poliovirus vaccines (OPVs) motivated the development of novel type 1 and 3 OPVs (nOPV1, nOPV3), designed to have similar safety and immunogenicity and improved genetic stability to reduce risk of reversion to neurovirulence. In this first-in-human trial, we assessed safety and immunogenicity of nOPV1 and nOPV3 in healthy adults. MethodsWe conducted a multi-site, randomized, observer-blind, controlled trial in healthy adults in the United States. Participants were stratified according to poliovirus vaccination history (exclusive inactivated polio vaccine [IPV] or including OPV) and randomized to receive either nOPV or homotypic Sabin-strain monovalent OPV (mOPV); IPV participants received a single dose and OPV participants received two doses. The primary objective was to assess safety measured by adverse events. The secondary objectives were to assess serum neutralizing antibody responses measured before and 28 days after each dose and fecal viral shedding assessed up to 56 days post-first dose. This study was registered with ClinicalTrials.gov, NCT04529538. FindingsBetween May 2021 and February 2023, 205 healthy adults were enrolled and received at least one dose: 70 nOPV1, 45 mOPV1, 56 nOPV3, and 38 mOPV3. Most events were mild, severe events were rare, and solicited events were balanced. Homotypic seroprotection was nearly 100% at baseline and was 100% after the first dose. Homotypic seroconversion rates after a single dose were high and similar for nOPV and mOPV (from 86 to 100%), with no statistically significant differences. Similar rates of viral shedding were observed among participants receiving nOPV or mOPV. InterpretationBoth nOPV1 and nOPV3 were well tolerated and demonstrated similar immunogenicity and shedding profiles to mOPV1 and mOPV3, respectively, supporting progression to phase 2 studies. nOPVs may be an important tool for achieving eradication of poliovirus. FundingGates Foundation. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSSabin-strain vaccine-derived polio virus (cVDPVs) and vaccine-associated paralytic polio (VAPP) are now a substantial proportion of paralytic poliomyelitis worldwide. To reduce the seeding of type 2 cVDPVs (cVDPV2), a more genetically stable novel oral polio vaccine (nOPV2) was developed to control outbreaks. WHO granted use under emergency use listing (EUL) in 2020 and prequalified the vaccine in 2023. More than one billion doses have been distributed since March 2021, with surveillance data demonstrating a promising safety and effectiveness profile. Sabin-strain types 1 and 3 present similar risks for cVDPVs and VAPP. In pre-clinical studies chimeric viruses with nOPV2s non-structural regions, including changes to the RNA sequence in the 5 untranslated region, the non-structural protein 2C, and the polymerase 3D, coupled with the coding region for the type-specific Sabin-strain capsid proteins have demonstrated similar immunogenicity, antigenicity, and lower neurovirulence compared to Sabin. Added value of this studyThis first-in-human trial includes safety and immunogenicity data in adults with a history of either exclusive inactivated polio vaccine (IPV) or prior exposure to OPV. We found that nOPV1 and nOPV3 are safe, well tolerated, and induce similar immunogenicity to their Sabin controls. The magnitude and durations of nOPV shedding was not higher than Sabin controls. We also observed induction of mucosal immunity, evidenced by reduced viral shedding post second vaccination. Implications of all the available evidenceThe successful deployment of nOPV2 to combat cVDPV2s previously demonstrated that use of such novel vaccines can be effective in the control of cVDPV outbreaks after the cessation of Sabin-strain types 1 and 3. nOPVs can thus support the polio endgame strategy by providing outbreak response vaccines less likely to be associated with VAPP and seeding of new cVDPVs. The safety and immunogenicity evidence generated for nOPV1 and nOPV3 in this phase 1 clinical study were sufficiently strong to justify phase 2 studies in geographically relevant target populations of previously vaccinated children and infants, as well as vaccine naive neonates.

BackgroundNearly 4 billion doses of the BioNTech-mRNA and Sinovac-inactivated vaccines have been administrated globally, yet different vaccine-induced immunity against SARS-CoV-2 variants of concern (VOCs) remain incompletely investigated. MethodsWe compare the immunogenicity and durability of these two vaccines among fully vaccinated Hong Kong people. FindingsStandard BioNTech and Sinovac vaccinations were tolerated and induced neutralizing antibody (NAb) (100% and 85.7%) and spike-specific CD4 T cell responses (96.7% and 82.1%), respectively. The geometric mean NAb IC50 and median frequencies of reactive CD4 subsets were consistently lower among Sinovac-vaccinees than BioNTech-vaccinees. Against VOCs, NAb response rate and geometric mean IC50 against B1.351 and B.1.617.2 were significantly lower for Sinovac (14.3%, 15 and 50%, 23.2) than BioNTech (79.4%, 107 and 94.1%, 131). Three months after vaccinations, NAbs to VOCs dropped near to detection limit, along with waning memory T cell responses, mainly among Sinovac-vaccinees. InterpretationOur results indicate that Sinovac-vaccinees may face higher risk to pandemic VOCs breakthrough infection. FundingThis study was supported by the Hong Kong Research Grants Council Collaborative Research Fund (C7156-20GF to Z.C and C1134-20GF); the National Program on Key Research Project of China (Grant 2020YFC0860600, 2020YFA0707500 and 2020YFA0707504); Shenzhen Science and Technology Program (JSGG20200225151410198 and JCYJ20210324131610027); HKU Development Fund and LKS Faculty of Medicine Matching Fund to AIDS Institute; Hong Kong Innovation and Technology Fund, Innovation and Technology Commission and generous donation from the Friends of Hope Education Fund. Z.C.s team was also partly supported by the Theme-Based Research Scheme (T11-706/18-N).

IntroductionThe spring 2023 COVID-19 booster vaccination programme in England used both Pfizer BA.4-5 and Sanofi vaccines. All people aged 75 years or over and the clinically vulnerable were eligible to receive a booster dose. Direct comparisons of the effectiveness of these two vaccines in boosting protection against severe COVID-19 events have not been made in trials or observational data. MethodsWith the approval of NHS England, we used the OpenSAFELY-TPP database to compare effectiveness of the Pfizer BA.4-5 and Sanofi vaccines during the spring 2023 booster programme, between 1 April and 30 June 2023. We investigated two cohorts separately: those aged 75 or over (75+); and those aged 50 or over and clinically vulnerable (CV). In each cohort, vaccine recipients were matched on date of vaccination, COVID-19 vaccine history, age, and other characteristics. Effectiveness outcomes were COVID-19 hospital admission, COVID-19 critical care admission, and COVID-19 death up to 16 weeks after vaccination. Safety outcomes were pericarditis and myocarditis up to 4 weeks after vaccination. We report the cumulative incidence of each outcome, and compare safety and effectiveness using risk differences (RD), relative risks (RR), and incidence rate ratios (IRRs). Results492,642 people were 1-1 matched in the CV cohort, and 673,926 in the 75+ cohort, contributing a total of 7,423,251 and 10,173,230 person-weeks of follow-up, respectively. The incidence of COVID-19 hospital admission was higher for Sanofi than for Pfizer BA.4-5. In the CV cohort, 16-week risks per 10,000 people were 22.3 (95%CI 20.4 to 24.3) for Pfizer BA.4-5 and 26.4 (24.4 to 28.7) for Sanofi, with an IRR of 1.19 (95%CI 1.06 to 1.34). In the 75+ cohort, these were 17.5 (16.1 to 19.1) for Pfizer BA.4-5 and 20.4 (18.9 to 22.1) for Sanofi, with an IRR of 1.18 (1.05-1.32). These findings were similar across all pre-specified subgroups. More severe COVID-19 related outcomes (critical care admission and death), and safety outcomes at 4 weeks, were rare in both vaccines so we could not reliably compare effectiveness of the two vaccines. ConclusionThis observational study comparing effectiveness of Pfizer BA.4-5 and Sanofi vaccine during the spring 2023 programme in England in the two main eligible cohorts - people aged 75 and over and in clinically vulnerable people - found some evidence of superior effectiveness against COVID-19 hospital admission for Pfizer BA.4-5 compared with Sanofi within 16 weeks after vaccination.

BackgroundSARS-CoV-2 variants, such as Alpha, Beta, Gamma and Delta, are raising concern about the efficiency of neutralizing antibodies (NAb) induced by wild-type infection or vaccines based on the wild-type spike. MethodsWe determined IgG and NAb against SARS-CoV-2 variants one year following mild wild-type infection (n=104) and two-dose regimens with BNT162b2 (BNT/BNT) (n=67), ChAdOx1 (ChAd/ChAd) (n=82), or heterologous ChAdOx1 followed by BNT162b2 (ChAd/BNT) (n=116). FindingsWild type spike IgG and NAb remained detectable in 80% (83/104) of unvaccinated participants one year post mild infection. The neutralizing capacity was similar against wild type (reference), Alpha (0.95 (0.92-0.98) and Delta 1.03 (0.95-1.11) but significantly reduced against Beta (0.54 (0.48-0.60)) and Gamma 0.51 (0.44-0.61). Similarly, BNT/BNT and ChAd/ChAd elicited sustained capacity against Alpha and Delta (1.01 (0.78-1.31) and 0.85 (0.64-1.14)) and (0.96 (0.84-1.09) and 0.82 (0.61-1.10) respectively), with reduced capacity against Beta (0.67 (0.50-0.88) and 0.53 (0.40-0.71)) and Gamma (0.12 (0.06-0.27) and 0.54 (0.37-0.80)). A similar trend was found following ChAd/BNT (0.74 (0.66-0.83) and 0.70 (0.50-0.97) against Alpha and Delta and 0.29 (0.20-0.42) and 0.13 (0.08-0.20) against Beta and Gamma). InterpretationPersistent neutralization of the wide-spread Alpha and Delta variants one year after wild-type infection may aid vaccine policy makers in low-resource settings when prioritizing vaccine supply. The reduced capacity of neutralizing Beta and Gamma strains, but not the Alpha and Delta strains following both infection and three different vaccine regimens argues for caution against Beta and Gamma-exclusive mutations in the efforts to optimize next generation SARS-CoV-2 vaccines. FundingA full list of funding bodies that contributed to this study can be found in the Acknowledgements section

BackgroundCOVID-19 vaccines with alternative strain compositions are needed to provide broad protection against newly emergent SARS-CoV-2 variants of concern. MethodsWe conducted a global Phase 3, multi-stage efficacy study (NCT04904549) among adults aged [&ge;]18 years. Participants were randomized 1:1 to receive two intramuscular injections 21 days apart of a bivalent SARS-CoV-2 recombinant protein vaccine with AS03-adjuvant (5 g of ancestral (D614) and 5 g of B.1.351 [beta] variant spike protein) or placebo. Symptomatic COVID-19 was defined as laboratory-confirmed COVID-19 with COVID-19-like illness (CLI) symptoms. The primary efficacy endpoint was the prevention of symptomatic COVID-19 [&ge;]14 days after the second injection (post-dose 2 [PD2]). ResultsBetween 19 Oct 2021 and 15 Feb 2022, 12,924 participants received [&ge;]1 study injection. 75% of participants were SARS-CoV-2 non-naive. 11,416 participants received both study injections (efficacy-evaluable population [vaccine, n=5,736; placebo, n=5,680]). Up to 15 March 2022, 121 symptomatic COVID-19 cases were reported (32 in the vaccine group and 89 in the placebo group) [&ge;]14 days PD2 with a vaccine efficacy (VE) of 64.7% (95% confidence interval [CI] 46.6; 77.2%). VE was 75.1% (95% CI 56.3; 86.6%) in non-naive and 30.9% (95% CI -39.3; 66.7%) in naive participants. Viral genome sequencing identified the infecting strain in 68 cases (Omicron [BA.1 and BA.2 subvariants]: 63; Delta: 4; Omicron and Delta: 1). The vaccine was well-tolerated and had an acceptable safety profile. ConclusionsA bivalent vaccine conferred heterologous protection against symptomatic infection with newly emergent Omicron (BA.1 and BA.2) in non-naive adults 18-59 years of age. ClinicalTrials.govNCT04904549

BackgroundVaccination with COVID-19 mRNA vaccines prevent hospitalization and severe disease caused by wildtype SARS-CoV-2 and several variants, and likely prevented infection when serum neutralizing antibody (NAb) titers were >1:160. Preventing infection limits viral replication resulting in mutation, which can lead to the emergence of additional variants. MethodsDuring a longitudinal study to evaluate durability of a three-dose mRNA vaccine regimen (2 primary doses and a booster) using a rapid test that semi-quantitatively measures NAbs, the Omicron variant emerged and quickly spread globally. We evaluated NAb levels measured prior to symptomatic breakthrough infection, in groups infected prior to and after the emergence of Omicron. ResultsDuring the SARS-CoV-2 Delta variant wave, 93% of breakthrough infections in our study occurred when serum NAb titers were <1:80. In contrast, after the emergence of Omicron, study participants with high NAb titers that had received booster vaccine doses became symptomatically infected. NAb titers prior to infection were [&ge;]1:640 in 64% of the Omicron-infected population, [&ge;]1:320 (14%), and [&ge;]1:160 (21%). DiscussionThese results indicate that high titers of NAbs elicited by currently available mRNA vaccines do not protect against infection with the Omicron variant, and that mild to moderate symptomatic infections did occur in a vaccinated and boosted population, although did not require hospitalization.

ImportanceWhether herd immunity through mass vaccination is sufficient to curb SARS-CoV-2 transmission requires an understanding of the duration of vaccine-induced immunity, and the necessity and timing of booster doses. Objective: To evaluate immune persistence of two priming doses of CoronaVac, and immunogenicity and safety of a third dose in healthy adults [&ge;]60 years. Design, setting, and participants: We conducted a vaccine booster study built on a single-center, randomized, double-blind phase 1/2 trial of the two-dose schedule of CoronaVac among healthy adults[&ge;]60 years in Hebei, China. We examined neutralizing antibody titres six months or more after the second dose in all participants. We provided a third dose to 303 participants recruited in phase 2 trial to assess their immune responses. InterventionsTwo formulations (3 g, and 6 g) were used in phase 1 trial, and an additional formulation of 1.5 g was used in phase 2 trial. All participants were given two doses 28 days apart and followed up 6 months after the second dose. Participants in phase 2 received a third dose 8 months after the second dose. Main outcomes and measuresGeometric mean titres (GMT) of neutralizing antibodies to live SARS-CoV-2 and adverse events were assessed at multiple time points following vaccination. ResultsNeutralizing antibody titres dropped below the seropositive cutoff of 8 at 6 months after the primary vaccination in all vaccine groups in the phase 1/2 trial. A third dose given 8 months or more after the second dose significantly increased neutralizing antibody levels. In the 3 g group (the licensed formulation), GMT increased to 305 [95%CI 215.3-432.0] on day 7 following the third dose, an approximately 7-fold increase compared with the GMT 28 days after the second dose. All solicited adverse reactions reported within 28 days after a booster dose were of grade 1 or 2 severity. Conclusion and relevanceNeutralizing antibody titres declined substantially six months after two doses of CoronaVac among older adults. A booster dose rapidly induces robust immune responses. This evidence could help policymakers determine the necessity and the timing of a booster dose for older adults. Trial registrationClinicalTrials.gov (NCT04383574).

SummaryHalf-dose AZD1222 or BNT162b2 boosters maintained immunogenicity and safety, and were non-inferior to full doses. All doses elicited high immunogenicity and best with extended post-CoronaVac primary-series intervals (120-180 days) and high-transmissibility Omicron. MethodsAt 60-to-<90, 90-to-<120, or 120-to-180 days ( intervals) post-CoronaVac primary-series, participants were randomized to full-dose or half-dose AZD1222 or BNT162b2, and followed up at day-28, -60 and -90. Vaccination-induced immunogenicity to Ancestral, Delta and Omicron BA.1 strains were evaluated by assessing anti-spike ( anti-S), anti-nucleocapsid antibodies, pseudovirus neutralization ( PVNT), micro-neutralization titers, and T-cells assays. Descriptive statistics and non-inferiority cut-offs were reported as geometric mean concentration (GMC) or titer (GMT) and GMC/GMT ratios comparing baseline to day-28 and day-90 seroresponses, and different intervals post-CoronaVac primary-series. Omicron immunogenicity was only evaluated in full-dose recipients. FindingsNo serious or severe vaccine-related safety events occurred. All assays and intervals showed non-inferior immunogenicity between full-doses and half-doses. However, full-dose vaccines and/or longer, 120-to-180-day intervals substantially improved immunogenicity (in GMC measured by anti-S assays or GMT measured by PVNT50; p <0.001). Within platforms and regardless of dose or platform, seroconversions were over 97%, and over 90% for pseudovirus neutralizing antibodies, but similar against the SARS-CoV-2 strains. Immunogenicity waned more quickly with half-doses than full-doses between day 60-to-90 follow-ups, but remained high against Ancestral or Delta strains. Against Omicron, the day-28 immunogenicity increased with longer intervals than shorter intervals for full-dose vaccines. InterpretationCombining heterologous schedules, fractional dosing, and extended post-second dose intervals, broadens population-level protection and prevents disruptions, especially in resource-limited settings. FundingFunding was provided by the Program Management Unit for Competitiveness Enhancement (PMU-C) National research, National Higher Education, Science, Research and Innovation Policy Council, Thailand through Clinixir Ltd. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSO_LIAlthough nAb titers from CoronaVac primary series waned after 3-4 months, nAb were more increased when boosted at 8 months than at 2 months post-primary series. C_LIO_LISix months post-vaccination with a one-fourth dose of primary mRNA-1273, nAb responses were half as robust as full doses, but VE was over 80% of that of full-dose vaccinations. C_LIO_LIThai adults boosted with 30g-BNT162b2 and 15g-BNT162b2 at 8-12 weeks after two-dose CoronaVac or AZD1222 had high antibodies to the virus receptor-binding domain, nAb titers against all variants, and T-cell responses. C_LIO_LIThird-dose boosting at a 44-45-week interval significantly increased antibody levels compared to boosting at 15-25-week or 8-12-week intervals. C_LIO_LIA third dose of CoronaVac administered eight months after the second dose increased antibody levels more than when administered at two months, while antibody responses were two-fold higher with a booster dose of AZD1222 administered at a 12-weeks or longer interval than a 6-weeks or shorter interval.Error! Bookmark not defined. C_LIO_LIIn the UK, third doses of AZD1222 led to higher antibody levels that correlated with high efficacy and T-cell responses, after a prolonged, dose-stretched interval between vaccine doses, than shorter intervals. C_LIO_LIOmicron-neutralizing antibodies were detected in only 56% of short-interval vaccine recipients versus all (100%) prolonged-interval vaccine recipients, 69% of whom also demonstrated Omicron-neutralizing antibodies at 4-6 months post-booster. C_LIO_LIIsraeli studies noted a restoration of antibody levels and enhanced immunogenic protection against severe disease when a second booster (fourth dose) was given 4 months or longer after a first booster, with no new safety concerns. C_LI Added value of this studyThere were no studies designed specifically aimed to analyzed non inferiority between the full dose and half dose of AZD1222 or BNT162b2 boosters after CoronaVac two doses which is important research question when we started the study and the situation of limited vaccine supply, global inequity and high disease burden in the Lower middle-income countries Data on the optimal prime-boost interval is limited, especially data that combines lower (fractional) dosing from resource-limited countries, which is provided by our study. Implications of all the available evidenceWe confirm the feasibility of a booster strategy that accounts for the needs of resource-limitations, through the use of fractional dosing, dose-stretching and heterologous schedules, which can broaden population-level protection and prevent vaccination disruptions.

BackgroundHuman infections with Japanese encephalitis virus (JEV) are a leading cause of viral encephalitis. An unprecedented outbreak of JEV genotype 4 was recently reported in Australia, with an isolate (JEVNSW/22) obtained from a stillborn piglet brain. MethodsHerein we compared the neuropathology of JEVNSW/22, JEVFU (genotype 2) and JEVNakayama (genotype 3) in adult C57BL/6J wild-type mice, mice deficient in interferon regulatory factor 7 (Irf7-/-), and mice deficient in type I interferon receptor (Ifnar-/-), as well as in human cortical brain organoids (hBOs). Using human serum post-Imojev vaccination, we performed neutralisation assays to determine JEVNSW/22 susceptibility to vaccine responses. FindingsIn C57BL/6J and Irf7-/- mice with lethal outcomes, brain infection and histopathological lesions recapitulated those seen in humans and primates. JEV was universally lethal in Ifnar-/- mice by day 3 with histological signs of brain hemorrhage, but produced no other detectable brain infection or lesions, with viral protein detected in blood vessels but not neurons. We thus describe a new Irf7-/- mouse model for JEVNSW/22, which had increased viremia compared to C57BL/6J mice, allowing for lethal neuroinvasive infection in one mouse. Overall, JEVNSW/22 was less neurovirulent than other JEV isolates in C57BL/6J and Irf7-/- mice, and was more sensitive to type I interferon. All JEV isolates showed robust cytopathic infection of human cortical brain organoids, albeit lower for JEVNSW/22. We also show that Imojev vaccination in humans induced neutralizing antibodies against JEVNSW/22, with the level of cross-neutralisation related to the conservation in envelope protein amino acid sequences for each isolate. InterpretationOur study establishes JEVNSW/22 mouse models of infection, allowing for possible lethal neuroinvasive infection that was rarer than for other JEV genotypes. JEV vaccination regimens may afford protection against this newly emerged JEV genotype 4 strain, although neutralizing antibody responses are sub-optimal. FundingQIMRB received a generous philanthropic donation from the Brazil Family Foundation awarded to D.J.R. to support Japanese Encephalitis virus research at QIMRB. A.S. holds an Investigator grant from the National Health and Medical Research Council (NHMRC) of Australia (APP1173880). We also acknowledge the intramural grant from QIMR Berghofer awarded to R.S. and D.J.R. for purchase of the CelVivo Clinostar incubator for producing human cortical brain organoids. The project "Japanese encephalitis vaccine via the intradermal route in children and adults (JEVID-2): A clinical trial comparing the immunogenicity and safety of Japanese encephalitis vaccine administered by subcutaneous and intradermal routes" being conducted by G.D., N.G., and N.W. was funded by the Sydney Childrens Hospitals Network and New South Wales Health. Research in context Evidence before the studyJEV from the historically rare genotype 4 recently emerged in Australia, causing an unprecedented outbreak, with 44 human cases and 7 fatalities. While a range of JEV mouse models have been reported, none of them infect adult mice with a genotype 4 isolate. The efficacy of current vaccines for this JEV genotype are also unclear. Added value of this studyWe establish well characterised adult and subcutaneously infected mouse models for JEV which recapitulate many aspects of human disease including lethal neuroinvasive infection and severe histopathological lesions. Prolonged viremia was significantly associated with lethal neuroinvasiveness in Irf7-/-mice. We demonstrate that a genotype 4 Australian isolate, JEVNSW/22, exhibited markedly diminished lethal neuroinvasion compared to other JEV genotypes. Using serum from Imojev vaccine recipients, neutralizing antibodies against JEVNSW/22 were present, albeit at sub-optimal titers. Implications of all the available evidenceThe establishment of well characterised adult mouse models of JEVNSW/22 with rare neuropenetrance after peripheral inoculation that recapitulate human disease is an important tool that can now be deployed in pre-clinical studies and to understand disease pathogenesis. Our study suggests that new vaccines should be developed against circulating JEV strains for optimal neutralizing antibody responses.