New England Journal of Medicine

Background Killed whole-cell oral cholera vaccines require multiple doses and have reduced efficacy in young children, limiting their utility. PanChol is a single-dose, oral live-attenuated cholera vaccine engineered from a current seventh pandemic El Tor O1 Vibrio cholerae strain. PanChol was shown to be safe and immunogenic in a previous phase 1a trial. In participants from this first-in-human trial, we aimed to assess the durability of the initial PanChol dose and the safety and immunogenicity of a second dose. Methods This open-label phase 1a booster study was conducted at Brigham and Women's Hospital (Boston, MA). Eligible participants were healthy adults aged 18-55 years without a history of cholera or gastrointestinal disorders and had received a PanChol dose ranging from 105-1010 colony-forming units (CFU) within the previous 322-1111 days. All participants received a booster dose of 2x107 CFU. The primary outcome was safety, including solicited, unsolicited, and serious adverse events following the second dose of PanChol. Secondary endpoints were the magnitude of pre- and post-vaccination serum vibriocidal titers to both Inaba and Ogawa V. cholerae, including seroconversion (4-fold rise in titers over baseline), and stool shedding of PanChol organisms using quantitative and qualitative stool cultures. Comparisons of the amount of vaccine shedding in stool following primary and secondary immunization were used to assess the intestinal mucosal immunity elicited by the initial PanChol dose. All outcomes were assessed in all participants. This trial is registered with ClinicalTrials.gov, NCT05657782, and is complete. Findings Between Aug 25, 2025, and Feb 20, 2026, 20 healthy adults who previously received a single oral dose of PanChol were enrolled to receive a booster dose of 2x107 CFU. Eleven (55%) of 20 participants were male and the median age was 43{middle dot}6 (IQR 30{middle dot}2-49{middle dot}5). Ten (50%) were White and 17 (85%) were not Hispanic or Latino. Nine (45%) of 20 boost recipients reported at least one solicited adverse event; 13 (93%) of 14 events were mild, and all were transient. The most common solicited adverse event was nausea, reported by 4 (20%) participants; all cases were mild. Most unsolicited adverse events were mild; one was grade 3 and was deemed unrelated to vaccination. Two unsolicited adverse events were deemed related to vaccination (mild gassy sensation and heartburn, both of which occurred on day 1 and resolved the same day). In most participants, vibriocidal antibody titers measured on the day of boosting exceeded baseline titers prior to the initial dose (17 (85%) for Inaba and 14 (70%) for Ogawa). Fifteen (75%) of 20 boost recipients seroconverted vibriocidal antibody titers to both serotypes. After the boost, 17 (85%) participants had no or self-limited vaccine shedding, compared with 10% after the first PanChol dose. Interpretation A second oral dose of PanChol had a favorable safety profile and induced vibriocidal seroconversion to both serotypes in 75% of boost recipients. Intestinal colonization of PanChol following the boost serves as a proxy for measuring mucosal immunity targeting V. cholerae. The decrease in in the abundance of PanChol fecal shedding following the second dose, compared with the first, suggests that a single dose of PanChol is sufficient to confer durable protective immunity against a cholera challenge. These observations underscore the need for further clinical development of PanChol. Funding Wellcome Trust.

SARS-CoV-2 antigenic evolution continues to challenge strain-matched vaccination. For the 2026-27 season, the European Medicines Agency (EMA) identified XFG as the preferred antigen within the JN.1 family and Comirnaty XFG was authorised in the European Union in July, 2026. We studied 22 participants who received 30 microg of mRNA encoding XFG (Comirnaty XFG, BioNTech/Pfizer, Mainz, Germany) in September, 2026 and had paired serum available before vaccination and median 14 days afterwards. Median Wuhan-Hu-1 S1-specific IgG increased from 1600 BAU/mL (IQR 1118-2926) to 2914 BAU/mL (2117-4468), a 1.8-fold increase. Median RBD-binding ED50 increased from 116 (51.4-212) to 305.6 (170.8-434.6) for LP.8.1 and from 354.3 (129.2-558.2) to 832.9 (429-1175) for NB.1.8.1, corresponding to 2.6-fold and 2.4-fold increases, respectively (all p<0.0001). XFG-adapted vaccination increased neutralising activity against each tested variant. The GMT against XFG increased from 180 before vaccination to 894 afterwards (5.0-fold), and that against RV.1.3 increased from 121 to 599 (4.9-fold). GMTs increased from 117 to 386 for PQ.16.1.1 (3.3-fold), from 101 to 316 for XFG.1.1 (3.1-fold), from 629 to 1772 for LP.8.1 (2.8-fold), from 221 to 611 for NB.1.8.1 (2.8-fold), and from 228 to 642 for PJ.2.1 (2.8-fold). Neutralisation of BA.3.2.2 increased more modestly, from GMT 78 to 126 (1.6-fold; p=0.0009). Pre- versus post-vaccination neutralisation titres differed significantly for all variants (p<0.001). Despite the broad increase, post-vaccination neutralisation remained heterogeneous. Relative to LP.8.1, GMTs were 2.0-fold lower for XFG, 2.8-fold lower for PJ.2.1, 2.9-fold lower for NB.1.8.1, 3.0-fold lower for RV.1.3, 4.6-fold lower for PQ.16.1.1, 5.6-fold lower for XFG.1.1, and 14.1-fold lower for BA.3.2.2. These findings provide early human immunogenicity data after XFG-adapted mRNA vaccination. The largest relative increases were observed for XFG and RV.1.3, whereas LP.8.1 remained the most strongly neutralised variant after Comirnaty XFG vaccination and BA.3.2.2 the least. This pattern suggests broad boosting of cross-reactive humoral immunity without elimination of between-variant differences. The small, extensively pre-immunised cohort, short follow-up, absence of a contemporaneous vaccine-comparator group, and use of a pseudovirus assay limit inference. Our data characterise early antibody binding and neutralisation but do not establish durability or clinical effectiveness.

The World Health Organization has called for malaria vaccines with > 90% efficacy against Plasmodium falciparum (Pf) infection. The live, non-attenuated PfSPZ-CVac (chloroquine) vaccine provides the strongest protection against controlled human malaria infection (CHMI). Its 100% protective efficacy at 12 weeks against genetically distant Pf stems from a highly amplified immune stimulus. After inoculation, each invading sporozoite (SPZ) replicates up to 50,000 times within a hepatocyte. Over six days of development, these parasites express thousands of distinct proteins, presenting a vast and diverse array of antigens to the host immune system. The late liver stage parasites then rupture into the bloodstream, where they are killed by the co-administered drug, chloroquine. To engineer a Pf parasite that develops to the late liver stage like PfSPZ-CVac (chloroquine), but then arrests before transitioning to the blood stage, two genes required for transition from non-pathogenic liver to pathogenic blood stages were identified and deleted, creating late-liver stage arresting, replication-competent (LARC) PfSPZ. In a first-in-human, randomized, double-blind, placebo-controlled clinical trial, we assessed PfSPZ-LARC2 Vaccine in 75 malaria-exposed Burkinabe 1- to 48-year-olds. No vaccine-strain breakthrough blood-stage infections were detected; safety and tolerability profiles were similar in vaccinees and placebo recipients; and the highest immunogenicity was observed in the youngest recipients. Based on these findings, PfSPZ-LARC2 Vaccine has progressed to Phase 2 testing with the goal of rapidly advancing this genetically attenuated whole parasite vaccine to licensure and deployment.

Importance Several influenza vaccine products are available for older adults, but evidence combining both their absolute effectiveness and head-to-head comparisons within the same large population remains scarce, limiting product-specific vaccination guidance for this high-risk group. Objective To estimate the relative and absolute effectiveness of influenza vaccines against influenza-related hospitalization and in-hospital mortality among older adults. Design, Setting, and Participants Nationwide cohort study using the French National Health Data System (SNDS), including all adults born in 1958 or earlier, living in metropolitan France, at the start of the 2023-2024 campaign. Relative effectiveness (rVE) was assessed using a landmark design with exposure fixed before epidemic onset. Absolute effectiveness (VE) was assessed using a sequential trial emulation with weekly matching of newly vaccinated individuals to yet unvaccinated controls. Follow-up ran from December 5, 2023 to April 19, 2024. Exposures Vaccination with a high-dose (Efluelda) or one of three standard-dose quadrivalent vaccines (Influvac, Fluarix, Vaxigrip), compared individually or by dosage category, and against no vaccination. Main Outcomes and Measures Hospitalization with a diagnosis of influenza and death during such hospitalization. Effectiveness was estimated as 1 minus the hazard ratio from weighted Cox models, with corresponding numbers needed to vaccinate to prevent one case. Results Among 13.8 million eligible individuals, 5.7 million (41%) were vaccinated at the beginning of follow-up. The high-dose vaccine showed greater rVE than standard-dose vaccines against hospitalization (27% [95%CI, 23 to 31%]) and in-hospital death (27% [95%CI,14 to 38%]). Absolute VE was 39% (95%CI, 38 to 41%) against hospitalization and 45% (95%CI, 40 to 49%) against in-hospital death, and was higher for the high-dose vaccine (50%) than standard-dose vaccines (36%) against hospitalization. This difference was most evident among adults 70 years and older, while overall effectiveness declined with age. Conclusions and Relevance In this study, influenza vaccination conferred moderate protection against severe outcomes in older adults, and high-dose vaccination was associated with significantly greater effectiveness than standard-dose vaccines, particularly among adults 70 years and older. These findings support product-level differentiation in vaccination strategy for this population.

Bundibugyo ebolavirus (BDBV) is causing an ongoing outbreak in the Democratic Republic of Congo (DRC) with no licensed vaccine available. Recent reports have shown the presence of BDBV-cross-reactive antibody responses in humans vaccinated against the related Ebola virus (EBOV). Here, we used an IFN-{gamma} ELISpot assay to assess T cell responses against the EBOV, BDBV and SUDV glycoproteins in clinical trial participants vaccinated with the licensed VSV-EBOV vaccine. We could show that BDBV-cross-reactive T cell responses are detectable in the majority of individuals and that conserved regions within the glycoprotein are targeted. In the absence of a BDBV-specific vaccine, these data support efficacy trials of the VSV-EBOV vaccine during the current outbreak.

Background: Global oral cholera vaccine (OCV) supply shortages and the retirement of Shanchol necessitate absolute reliance on alternative formulations. We conducted a systematic review and meta-analysis to evaluate the immunogenicity and safety of Euvichol variants compared with the historical Shanchol benchmark. Methodology/Principal Findings: A searched PubMed, Embase, MEDLINE, Scopus, and Cochrane CENTRAL up to May 2026 for randomized controlled trials (RCTs) comparing any Euvichol variant against Shanchol in healthy populations aged [&ge;]1 year. Primary outcomes were vibriocidal seroconversion rates at 14 days post-dose 2 pooled as Risk Ratios (RRs) via Mantel-Haenszel fixed-effects models. Five RCTs comprising 7,253 participants were included. Euvichol formulations demonstrated non-inferior, equivalent seroconversion rates compared with Shanchol for both Vibrio cholerae O1 Inaba (RR 1.00, 95% CI 0.98-1.02; I2=0%) and O1 Ogawa (RR 1.01, 95% CI 0.99-1.04; I2=26%). Log-transformed Geometric Mean Titers confirmed clinical equivalence for Inaba (MD 0.02, 95% CI -0.01 to 0.05) and Ogawa (MD 0.00, 95% CI -0.03 to 0.03). Overall safety was balanced between arms, showing no significant variation in the risk of any solicited adverse event (RR 0.91, 95% CI 0.75-1.11) or specific symptoms including fever (RR 0.84, 95% CI 0.52-1.35). Serious adverse events were rare and uniformly unrelated to vaccination. Conclusions/Significance: Euvichol variants demonstrate immunogenic non-inferiority and interchangeable safety thresholds compared with Shanchol. These findings robustly support the large-scale integration of modern Euvichol-Plus and streamlined Euvichol-S formulations to stabilize global OCV stockpiles.

Nicotinamide riboside (NR), an endogenous precursor to the essential coenzyme nicotinamide adenine dinucleotide (NAD+), is characterized as safe and effective for longitudinally elevating NAD+ in blood and tissues, when administered orally. Interest in alternative routes of administration of NR has increased in recent years and led to the development of pharmaceutical-grade NR for intravenous and injectable administration. To evaluate the safety and efficacy of repeat daily injections of NR, an open-label, pilot, trial was initiated. Utilizing a 2x2 parallel study design, 39 study participants were randomized to intramuscular (IM) or subcutaneous (SC) injection administration, and 50 or 100 mg of NR, for 3 consecutive days, followed by a 7-day washout (50 mg IM, n=7; 100 mg IM, n=11; 50 mg SC, n=11; and 100 mg SC, n=10). To assess the primary outcome of safety, vitals, blood biomarkers, and adverse event monitoring were employed. Additional assessments included NAD+ pharmacokinetics and subjective participant-reported outcomes. Daily injections of NR were well tolerated and did not result in any unexpected adverse events or experiences. Pain and muscle soreness/tightness more than two minutes after the injection were reported by 44% and 41% of the participants, respectively, regardless of the route of administration or dose. Significant heterogeneity of pharmacokinetic parameters for NAD+ augmentation of whole blood was observed, however an average of the daily percentage increases in NAD+ was consistent across treatment groups, resulting in 9.51, 9.97, 7.83, and 9.05% for 50 mg IM, 100 mg IM, 50 mg SC, and 100 mg SC, respectively. Exploratory participant-reported outcomes suggest potential benefits on fatigue and sleep, with mixed effects on global physical health. Repeat daily injections of NR were well tolerated, and findings warrant investigation in larger, powered, placebo-controlled trials.

Background: Recombinant (RIV) and cell culture-based inactivated (ccIIV) influenza vaccines could improve seasonal influenza prevention; however, evidence is limited in how protection may differ among non-egg-based vaccines. Methods: We conducted a randomized trial of RIV versus ccIIV to compare vaccine immunogenicity in adults aged 18 to 64 years during the 2024-25 influenza season (ClinicalTrials.gov, NCT06518577). Active surveillance for influenza-like illness was conducted for six months post-vaccination and cumulative incidence of influenza by vaccine type was compared to estimate relative vaccine efficacy. Participants were tested for influenza by reverse-transcription polymerase chain reaction or rapid antigen tests. Immunogenicity was evaluated by hemagglutination inhibition (HAI), virus microneutralization (MN), and neuraminidase inhibition (NAI) assays in a subset of blood specimens collected pre-vaccination and one-month post-vaccination. Results: Among the 591 participants, 25 cases of influenza A were detected; 2.4% cumulative incidence among RIV recipients versus 6.1% among ccIIV recipients. The probability of influenza was 61% lower with RIV than ccIIV (95% confidence interval: 7 to 84). Among 151 participants, post-vaccination HAI and MN titers vaccine components were higher among RIV recipients while NAI titers were higher among ccIIV recipients. Conclusions: RIV provided better protection than ccIIV against influenza A illness in adults during the U.S. 2024-2025 season.

The Democratic Republic of the Congo is experiencing a major outbreak of Ebola disease caused by Orthoebolavirus bundibugyoense (Bundibugyo virus), which was declared on May 15, 2026. To investigate the timing of emergence and early transmission, we generated near full length Bundibugyo virus genomes from 686 PCR-confirmed individuals across 22 health zones. We estimated the time of emergence as late February 2026 (95% highest posterior density interval [HPDI]: January 21 and March 25, 2026) and an evolutionary rate of 8.7X10-4 substitutions per site per year (95% HPDI: 7.6 and 9.9X10-4), with no evidence of mutations associated with rapidly growing lineages.

Low pathogenic avian influenza A(H7N7) virus detected in a poultry worker in Taiwan, 2026 was related to viruses circulating in Asian wild birds and possessed PB2 E627K, a mammalian adaptation marker. Enhanced surveillance for H7 viruses in poultry and rapid characterization of human cases are essential to assess pandemic potential.

BackgroundHuman Mastadenovirus B (HAdV-B) causes ocular and respiratory infections and is capable of causing outbreaks in healthcare settings. HAdV-B114, a recombinant genotype only formally recognised in 2023, has been reported predominantly from Germany, the USA, China and Japan; genomic data from UK clinical settings remain limited. This study analysed 68 HAdV-B whole genomes from ocular and respiratory-associated samples collected at a Nottingham hospital across the pre- and post-COVID-19 restriction periods (2017-2023). MethodsClinical samples typed positive for HAdV-B by partial hexon Sanger sequencing were selected for whole-genome sequencing using a novel overlapping PCR amplicon strategy, sequenced on the Oxford Nanopore Technologies PromethION platform. Phylogenetic and pairwise difference analyses were used to characterise genotype composition and genomic relatedness. SimPlot and amino-acid comparison characterised divergence between sub-lineages. ResultsWhole-genome phylogenetics confirmed that two species B genotypes were detected in Nottingham University Hospitals between 2017-23: HAdV-B114 (n=56) and HAdV-B7 (n=12). HAdV-B114 was detected before and after COVID-19 restrictions, with an increase in 2022-2023, consistent with post-restriction expansion of a pre-existing lineage. Pairwise difference analysis identified 24 genomically identical B114 sequences; associated metadata argued against a single nosocomial transmission chain interpretation, with the pattern more consistent with repeated detection of a widely circulating community strain, with the possibility of localised onward transmission. Within the B114 clade, multiple monophyletic groups were identified by whole-genome phylogenetics. ConclusionsThis study adds whole-genome resolution to the existing UK HAdV-B114 data, demonstrates the utility of WGS for clinical adenovirus surveillance and shows the benefits of combining epidemiological data with genomic analysis.

Nicotinamide riboside (NR), a precursor to the essential coenzyme nicotinamide adenine dinucleotide (NAD+), has been extensively studied following oral administration, while the longer-term safety and physiological effects of injectable NR remain less characterized. Following an initial in-clinic phase evaluating repeat intramuscular (IM) and subcutaneous (SC) administration of pharmaceutical-grade NR, participants transitioned to an at-home phase designed to assess the safety, feasibility, and exploratory physiological effects of repeated self-administered SC administration. Participants continued their assigned 50 or 100 mg dose group and self-administered NR subcutaneously 3 times weekly for approximately 90 days. Safety was assessed through adverse event (AE) monitoring, vital signs, and clinical laboratory health measures. Exploratory assessments included markers of mitochondrial bioenergetics, urinary biomarkers of oxidative stress, and participant-reported outcomes related to fatigue, sleep, pain, and quality of life. At-home administration of NR was generally well-tolerated, with no clear dose-dependent safety concerns identified over the study period. Further, participants were able to successfully self-administer repeated SC injections over the study period, demonstrating positive feasibility. Whole-blood NAD+ concentrations remained largely stable over time in both dose groups. MeScreen analysis demonstrated a reduction in GlycoATP at Day 30 and increases in the MitoATP/GlycoATP ratio at Day 30 and Day 90, signifying a preferential shift toward oxidative metabolism. These findings may be indicative of positive metabolic health shifts. Urinary oxidative stress profiling demonstrated heterogeneous temporal responses. Several lipid oxidation markers significantly declined at Day 30 but returned toward baseline at Day 90. Select markers of nucleic acid, nitrative stress, and advanced glycation end-product oxidation demonstrated more sustained reductions. These results for which the majority of measured oxidative stress markers improved suggest that NR injections may exhibit anti-oxidative characteristics. Validated participant-reported sleep and fatigue measures showed improvements. Self-reported facial skin improvement increased descriptively from 11.4% at baseline to 27.8% at Day 30 and 36.8% at Day 90; improvements noticed by others increased from 9.1% to 23.7%, while reported body-skin improvement increased more modestly, from 8.8% to 16.7%. As these outcomes were not designed or powered to establish efficacy or definitive clinical claims, the findings should be considered hypothesis generating and provide preliminary data to inform the selection of outcomes and design considerations for future randomized, placebo-controlled, adequately powered trials of SC NR administration.

Since emerging in 2020, clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus (HPAIV) has disseminated globally, causing substantial infection and mortality in wild birds and poultry. Additionally, numerous spill-over events into mammals have occurred, including mass mortalities and sporadic human infections. Such events can drive the acquisition of mammalian-adaptive mutations, which further increase the risk to humans; the most well characterised mutation is the glutamate to lysine change at amino acid position 627 in the polymerase basic 2 protein (PB2-627K). Across avian influenza viruses, PB2-627K enhances polymerase activity and replication in mammalian cells, increasing zoonotic and pandemic potential. However, bioinformatic analyses indicate that PB2-627K remains rare among clade 2.3.4.4b H5N1 viruses circulating in avian populations. Here, we investigated the impact of PB2-627K on viral fitness in avian hosts to assess the potential for mammalian-adapted viruses to re-establish in birds, mimicking infection of avian species following scavenging on mammalian species where PB2-627K has already emerged. Using a representative H5N1 virus (European genotype AB), PB2-627K increased polymerase activity and replication in human cells without compromising replication in avian cells. A mammalian-derived PB2-627K H5N1 isolate from a fox exhibited comparable replication kinetics and transmission efficiency in chickens and ducks to a closely related PB2-627E virus. Notably, PB2-627K remained genetically stable at consensus level following infection and transmission in both avian hosts. These findings demonstrate that mammalian-adaptive mutations acquired during spill-over can be maintained in avian populations, potentially elevating zoonotic risk and underscoring the importance of surveillance for such mutations in birds.

Background: Filoviruses, specifically Ebola virus (EBOV), Bundibugyo virus (BDBV), and Marburg virus (MARV), have been the etiologic agents of multiple outbreaks of severe disease in the Democratic Republic of the Congo (DRC). Two EBOV-specific vaccine regimens have been approved for use in outbreak scenarios, including the Ad26.ZEBOV/MVA-BN-Filo (Zabdeno/Mvabea) two-dose vaccine, where the MVA-BN-Filo booster dose contains EBOV, MARV, and Sudan (SUDV) virus glycoproteins (GPs) and the nucleoprotein from Tai Forest virus. While long-term immunogenicity of up to two years has been found in clinical trial settings, limited real-world data exists. Methods: Using a multiplexed immunoassay, samples (n=698 at baseline) collected in Mbandaka, Equateur province, DRC, between September 2023 and October 2024 were assessed for seroreactivity to six filovirus antigens (1 BDBV, 2 EBOV, 2 MARV, and 1 SUDV) at three distinct periods: baseline/pre-vaccination, 6-8 weeks post-first dose (Zabdeno), at booster administration (Mvabea), and one-year post-boost dose. Results: Substantial filovirus seroreactivity was found at baseline, with 48.7% (n=340/698) of individuals being seroreactive to at least one virus antigen. High baseline seroreactivity was found against BDBV GP (31.1%, n=217/698), with lower baseline seroreactivity to EBOV GP (15.5%, n=106/698), comparatively. Overall EBOV GP seroreactivity increased to 66.8% (n=376/563) at one year-post vaccine boost and 57.6% (n=250/434) of participants were seroreactive. Despite the booster dose inclusion of SUDV GP and MARV GP, there were no substantial increases in reactivity against either antigen at subsequent timepoints. Overall filovirus seroreactivity increased at all timepoints for the entire cohort, although filovirus reactivity decreased over the study period for those who were seroreactive at baseline. Findings: These data highlight detection of significantly elevated seoreactivity to EBOV GP following first-dose administration of Ad26.ZEBOV, which remained relatively stable one-year post-booster dose administration. Additionally, this study identifies high levels of baseline seroreactivity to BDBV GP despite no previous documented outbreaks in this region of DRC. These data suggest that vaccination with the Ad26.ZEBOV-MVA-BN-Filo vaccine induces stable seroreactivity against EBOV GP, but not to other filovirus antigens.

Background Ecological surveillance indicates (regional) establishment of West Nile virus (WNV) and Usutu virus (USUV) in the Netherlands. However, the incidence of human infections remains unknown. Methods We identified WNV and USUV infections in the Netherlands in 2020-2023, using a longitudinal, nationwide population-based cohort, applying a two-tiered serology approach based on protein micro-array and virus neutralization. IgG data were used to estimate overall seroprevalence and infection incidence, and to study antibody longevity. Study set-up enabled tracking of the period of seroconversion and linking of self-reported travel history. The analyses took account of the survey design and weights were incorporated to match the Dutch population distribution following census data. Findings Among 4290 participants, we identified 113 probable WNV and/or USUV cases, including 55 seroconversions. Thirty-six cases were confirmed by antibody neutralization, of which 12 seroconverted. Six confirmed seroconverters were identified as autochthonous infections. The overall weighted seroprevalence was estimated at 0.54% (0.21-0.87%) for WNV and 0.25% (0.09-0.40%) for USUV. The weighted incidence for autochthonous WNV and USUV infection was estimated as respectively 0.06% (95% CI 0-0.12%) and 0.04% (95% CI 0-0.09%). Interpretation The estimated infection incidence and seroprevalence of WNV and USUV indicate a substantial underdiagnosis of clinical cases in the Netherlands in 2020-2023. These observations highlight the need for increased awareness among physicians to identify cases and the need for continued paired syndromic-laboratory surveillance for these viruses.

Objectives- Among clinical methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) strains, we sought to determine the prevalence of {beta}-lactam-{beta}-lactamase inhibitor (BLBLI) susceptibility, and its association with oxacillin susceptibility, genotypic factors, and patient characteristics. Methods- Clinical MRSA BSI strains were tested for susceptibility to penicillin-clavulanate by Etest (n=117, 36% of the dataset) and to oxacillin by disk diffusion assay (n=328, 100%). Penicillin-clavulanate susceptibility was defined as MIC [&le;]2mg/L and oxacillin disk susceptibility as an inhibition zone > 6mm. All strains were whole-genome sequenced, and alleles of mecA annotated. The sensitivity and specificity of the oxacillin disk to predict penicillin-clavulanate 'susceptibility' were assessed. Clinical and genomic associations with BLBLI 'susceptibility' were assessed by calculating odds-ratios (OR). Results -We found 73/117 (62%) and 205/328 (62%) strains to be 'susceptible' to penicillin-clavulanate and oxacillin disk, respectively. Oxacillin disk susceptibility and penicillin-clavulanate susceptibility were highly correlated (sensitivity 97.3% and specificity 95.5%). We therefore used oxacillin disk susceptibility as a proxy for penicillin-clavulanate susceptibility. Comparative genomics of the mecA gene uncovered 8 alleles. The oxacillin disk 'susceptible' phenotype was associated with specific mecA alleles, community-associated MRSA sequence-types (OR 72.8, 95%CI 35.4-162), community acquisition of infection (OR 2.09, 95% CI 1.03-4.27), lower Charlson Comorbidity Index (OR 0.90, 95% CI 0.82-0.98) and SOFA (sequential organ failure assessment) scores at presentation (OR 0.88, 95% CI 0.79-0.98). Conclusion - BLBLI 'susceptibility' is common among MRSA strains and is strongly associated with the strain genotype. Infections caused by BLBLI 'susceptible' strains are associated with specific patients' characteristics, namely younger age, fewer comorbidities, acquisition in the community and milder presentations.

Since 2020, highly pathogenic avian influenza (HPAI) A(H5Nx) clade 2.3.4.4b viruses have spread globally, causing extensive outbreaks in domestic and wild birds. Increased circulation has resulted in frequent spillover to mammals, and occasional mammal-to-mammal transmission. Although human infections remain rare, the zoonotic potential of these viruses continues to be a public health concern. We investigated six cases of HPAI in red foxes (Vulpes vulpes) in Norway during 2022-2024 and identified infections with H5N1 and H5N5 viruses. Pathological and virological investigations demonstrated systemic infection, with prominent lesions in the brain and/or lungs. Phylogenetic analyses showed high similarity between viruses detected in foxes and those concurrently circulating in wild birds. The mammalian adaptation marker PB2:E627K was identified in one H5N1 virus and as a minority variant in a second H5N1 virus.

There is currently no clinical data for the effectiveness of the only licensed Ebola virus disease vaccine (Ervebo) against Bundibugyo virus disease. A number of studies have shown immune cross-reactivity with Bundibugyo virus after Ervebo vaccination. However, antibody recognition of Bundibugyo is around 2.8-fold lower than recognition of Ebola virus. Here, we aimed to infer how a 2.8-fold drop in immune recognition may affect Ervebo protection against Bundibugyo virus disease based on analysis of data on Ervebo immunogenicity and protection from Ebola virus disease. This work has three main components. Firstly, we analysed the timing of vaccine protection in the Ervebo pivotal ring vaccination clinical trial. Secondly, we performed a systematic review and meta-analysis of antibody responses to Ebola virus after Ervebo vaccination over time. Thirdly, we combined these data with previously reported data on the cross-reactivity to Bundibugyo virus to infer protection of Ervebo against Bundibugyo virus disease. We find that the clinical trial data for Ervebo supports vaccine protection beginning earlier than 10 days after vaccination. Secondly, binding antibody levels against Ebola virus on day 28 post vaccination (peak responses) were on average 12.9-fold (95% confidence interval, CI: 6.4 - 26.0) higher than on day 7, 6.3-fold (95% CI: 3.7 -10.8) higher than on day 10, and 2.5-fold (95% CI: 1.4 - 4.4) higher than on day 14 (neutralising antibodies showed similar results). Finally, we consider the scenarios where antibody levels to Ebola virus at day 7 or 10 are putative protective thresholds against Ebola virus disease, and we assume these thresholds also apply for Bundibugyo virus disease. Then, with a 2.8-fold reduction of responses to Bundibugyo compared to Ebola virus, we predict antibody responses to Bundibugyo virus after Ervebo vaccination are likely above these putative protective thresholds.

The emergence of a dominant poultry-associated strain of Campylobacter jejuni in New Zealand coincided with a multi-year epidemic of human campylobacteriosis. This was characterised by an increase in cases to 2006, when one of the highest national case-rates in the world was recorded, followed by a rapid decline attributed to interventions in the poultry industry. The strain belonged to an internationally rare multilocus sequence type, ST474 - a member of Clonal Complex (CC) 48 - that was highly prevalent in both poultry and human cases in New Zealand but was also identified in other samples. ST474 isolates from humans, animal reservoirs and environmental water samples were collected between 2005 and 2019 and whole genome sequenced (N=443). Isolates from a 2018/9 case-control study of campylobacteriosis in New Zealand were included for genomic comparisons with other sequence types and CCs. This presented an opportunity to examine the genomic epidemiology of a single, relatively recently emerged lineage of C. jejuni, and improve our understanding of drivers of emergence and persistence in a relatively isolated ecosystem. Six subpopulations (clades) of ST474 were identified and these varied in terms of their host association, persistence, patterns of homologous recombination, and complement of mobile genetic elements, including plasmids and chromosomally integrated elements. Clade E was associated with a single poultry supplier in the initial epidemic phase and accounted for 34.5% of human cases. Clade F emerged from a declining Clade E after the peak in human cases and was also associated with poultry. The emergence of Clade F was accompanied by the loss of integrated element CJIE5 and the acquisition of multiple blocks of recombination, likely from diverse ancestral C. jejuni lineages, and the loss of the methionine biosynthesis operon metAB. In contrast, Clades A-D were detected at low frequencies in human cases over the 14-year period of surveillance and were associated with multiple hosts. This longitudinal study sheds light on the evolutionary processes that result in strain emergence and differentiation, highlighting the role of horizontal gene transfer in the evolution and adaptation of this pathogen to new niches, and the subsequent impact on public health.

Haemophilus influenzae is a Gram-negative bacterium that causes pneumonia, otitis media, and invasive infections such as meningitis and bacteremia. A vaccine that confers protection against disease caused by H. influenzae serotype b is currently available and is highly effective, but infections caused by non-b serotypes and non-typeable strains are still prevalent and increasing, suggesting a need for a broadly cross-protective vaccine that will protect against infection by all H. influenzae strains. To address the need for broad cross-protection, this study focused on the surface lipoprotein component of the bipartite bacterial transferrin receptor, transferrin binding protein B (TbpB), which is universally present H. influenzae, irrespective of encapsulation status, and is essential for bacterial colonization and pathogenesis. To prevent vaccine escape, we assessed the sequence and structural diversity among TbpB variants derived from local and international H. influenzae isolates and observed that these sequences cluster independently of encapsulation status, suggesting that conferring protection against all H. influenzae strains regardless of capsule type or presence of a capsule using a TbpB-based vaccine is feasible. In addition, our diversity analysis also revealed that the C-terminal lobe (C-lobe) of TbpB contains several large, highly variable loops. After immunizing mice with a trivalent vaccine consisting of a representative set of TbpB variants, we found that the resulting antiserum demonstrated modest cross-reactivity against heterologous TbpB variants. However, immunizing with a loopless C-lobe (LCL) that lacks the large, highly variable loops we had identified elicited broad cross-reactivity against a panel of intact TbpB variants. This suggests that while the intact TbpB may only generate a moderately cross-reactive antibody response, a vaccine consisting of a single LCL may be able to elicit a sufficiently cross-reactive humoral response against diverse TbpB variants, and in turn, confer broad cross-protection targeting both encapsulated and non-typeable H. influenzae.