The Lancet

BackgroundIn England, the burden of respiratory infections varies by ethnicity, contributing to health inequalities, but the role of additional demographic factors remains underexplored. We quantified how differences in social mixing and demographic characteristics between ethnic groups cause inequalities in transmission dynamics. MethodsWe analysed the association between the ethnicity and the number of contacts of 12,484 participants in the 2024-2025 Reconnect social contact survey, using a negative binomial regression model. We simulated respiratory pathogen epidemics using a compartmental model stratified by age, ethnicity, and contact levels, at a national level and in major cities in England. FindingsAfter adjusting for demographic variables, participants of Black and Mixed ethnicities had more contacts than those of White ethnicity (rate ratios (RR): 1.18 [95% Credible Interval (CI): 1.11-1.26], and 1.31 [95% CI: 1.14-1.52]). Participants of Asian ethnicity had fewer contacts (RR: 0.85 [95% CI: 0.79-0.91]). In national-level simulations, individuals of White ethnicity had the lowest attack rates due to demographic differences and mixing patterns. Local demographic structures changed simulated dynamics: attack rates in individuals of Black and Mixed ethnicities were approximately double those of White ethnicity in Birmingham, but less than 60% higher in Liverpool. InterpretationDemographic characteristics and mixing patterns create inequalities in transmission dynamics between ethnicities, while local demographic characteristics and pathogen infectiousness change the expected relative burden. To ensure mitigation strategies are effective and equitable, their evaluation must explicitly account for inequalities arising from local context. FundingMedical Research Council, National Institute for Health and Care Research, Wellcome Trust Research in context Evidence before this studyWe searched PubMed for population-based studies quantifying differences in respiratory infections between ethnic groups, up to 1 April 2026, with no language restrictions. Keywords included: (respiratory pathogens OR influenza OR COVID-19) AND (ethnic* OR race) AND (inequ*) AND (compartmental model OR incidence rate ratio OR hazard ratio). We excluded studies that focused on non-respiratory pathogens (e.g. looking at consequences of COVID-19 on incidence of other pathogens). A population-based cohort study showed that influenza infection risk was higher in South Asian, Black, and Mixed ethnic groups compared to White ethnicity in England. Another population-based cohort study highlighted that during the first wave of COVID-19 in England, the South Asian, Black, and Mixed ethnic groups were more likely to test positive and to be hospitalised than the White ethnic group. Census data in England showed that the distributions of age, household size, household income and employment status differed between ethnic groups, and the recent Reconnect social contact surveys highlighted the impact of each demographic factor on the participants number of contacts. Added value of this studyOur study shows that social contact patterns, mixing, and demographic structure all lead to unequal infection risk between ethnic groups in respiratory pathogen epidemics. Using the largest available social contact survey in England, we show that both the average number of contacts and the proportion of high-contact individuals varied by ethnic group, even after adjusting for participants demographics. These differences, together with mixing patterns and age structure, led to lower expected incidence among individuals of White ethnicity than in all other ethnic groups in simulated outbreaks. The level of inequality between ethnic groups changed when we used different values of pathogen transmissibility. Finally, as ethnic composition and population structure differ between cities in England, our results show differences in expected inequalities at a local level. Implications of all the available evidenceInequalities in infection risk between ethnic groups are context- and pathogen-dependent. They arise from both local population structure and contact patterns. Detailed information on mixing between groups and population structure is needed to accurately measure group-specific infection risk. These findings indicate that public health interventions based only on national-level estimates conceal regional variation in risk and may ultimately increase inequalities. Public health interventions need to be tailored to local contexts to be equitable and effective. Finally, our findings provide a foundation for understanding the progression from infection-risk inequalities to disparities in disease presentation and clinical outcomes.

BackgroundIn England, individuals with chronic liver disease (CLD) are among those with the lowest seasonal influenza vaccine uptake despite being at elevated risk of severe influenza. We examined the relationship between CLD severity and aetiology, and influenza vaccine uptake in England. MethodsA retrospective cohort study of adults (18-115 years) using Clinical Practice Research Datalink Aurum primary care data was conducted for five seasons (2019/20-2023/24). Poisson regression was used to estimate rates of uptake by CLD severity (clinical diagnoses categorised as low, moderate, or severe) and aetiology (alcohol-related, viral-related, and diagnoses in the Green Book guidelines). FindingsThere were 182,174-277,470 with CLD per cohort. Among those who were additionally age-eligible for vaccination, uptake was 71{middle dot}1-79{middle dot}7% compared to 30{middle dot}9-40{middle dot}5% in those not additionally age-eligible. Among individuals below age eligibility without other comorbidities, severity was associated with higher uptake (incidence rate ratio [IRR] moderate 1{middle dot}80, 95% CI 1{middle dot}69-1{middle dot}90; severe 1{middle dot}95, 95% CI 1{middle dot}84-2{middle dot}08 in 2023/24); there was no effect in those with at least one additional comorbidity (moderate 1{middle dot}05, 95% CI 0{middle dot}99-1{middle dot}10; severe 1{middle dot}05, 95% CI 1{middle dot}01-1{middle dot}09). Alcohol- and viral-related aetiology were also associated with increased uptake in those not additionally age-eligible. Among individuals meeting age eligibility without additional comorbidities, severity was associated with a reduced uptake (moderate 0{middle dot}81, 95% CI 0{middle dot}73-0{middle dot}90; severe 0{middle dot}79, 95% CI 0{middle dot}74-0{middle dot}85), with attenuation in those with additional comorbidities (moderate 0{middle dot}99, 95% CI 0{middle dot}94-1{middle dot}04; severe 0{middle dot}91, 95% CI 0{middle dot}89-0{middle dot}94). InterpretationCLD severity and aetiology were important determinants of uptake in the absence of additional indications for influenza vaccination. Future research should prioritise understanding facilitators and barriers to vaccine uptake in individuals with CLD, particularly for those at highest risk of severe infection. FundingNIHR Health Protection Research Unit in Vaccines and Immunisation (NIHR200929/NIHR207408). Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWe searched PubMed up to June 2025 using the terms "chronic liver disease", "cirrhosis", "hepatitis", "influenza vaccination", "seasonal influenza", and "vaccine uptake". Previous research, including national data from England, has shown that people with chronic liver disease tend to have lower seasonal influenza vaccine uptake than individuals with other medical comorbidities which qualify for vaccination such as diabetes, chronic kidney disease or immunosuppression. The reasons for low influenza vaccine uptake in people with chronic liver disease are not well understood, and it is therefore difficult for vaccination providers, principally primary care services in England, to tailor interventions aimed to increase uptake. Qualitative research involving individuals aged less than 65 years living in England with clinical risk comorbidities, most commonly diabetes, found that chronic disease management pathways inconsistently provided information about the importance of influenza vaccination as part of chronic disease management. Individuals with long-term conditions reported low perceived risk of influenza infection and limited awareness of vaccine benefits as important reasons for non-uptake. We hypothesised that the severity and aetiology of chronic liver disease may be important determinants of uptake. Added value of this studyWe conducted a population-based study to examine how chronic liver disease severity and aetiology influence seasonal influenza vaccine uptake in adults in England. Using primary care electronic health record data from five consecutive influenza seasons (2019/20-2023/24), we found that more severe chronic liver disease was associated with a substantial increase in vaccine uptake in those without additional indications for seasonal influenza vaccination (age-based eligibility or other qualifying clinical risk comorbidities). Alcohol- and viral-related aetiology were also associated with increased uptake in those who were not additionally age-eligible for vaccination. In contrast, severity, alcohol- and viral-related underlying aetiology were associated with a modest reduction in uptake for individuals with chronic liver disease who also qualified for vaccination due to age. Implications of all the available evidenceDespite clear clinical vulnerability to infection and a substantially elevated risk of morbidity and mortality following infection, a large proportion of adults with chronic liver disease, particularly those aged under 65 years, remain unvaccinated against seasonal influenza each year. This study suggests that chronic liver disease severity and underlying aetiology are important determinants of uptake in individuals not meeting age-based vaccine eligibility, particularly in those without additional clinical risk comorbidities. This could be because of differing perceptions of influenza risk, or due to varying degrees of interaction with healthcare specialists as part of chronic disease management. In individuals who met age-based vaccination eligibility, the negative effect of severity on influenza vaccine uptake may reflect greater barriers to accessing vaccination services by those with more complex health needs, or competing medical priorities for long-term condition management during consultations. To inform targeted vaccination strategies, future research should aim to understand the specific facilitators and barriers to influenza vaccination experienced by individuals with chronic liver disease. This should include perspectives of individuals with different disease severity, across different age groups, in those with and without additional co-morbidities.

Background: The 2024-25 influenza season was the most severe in the United States (US) since 2017-18, with co-circulation of both influenza A virus subtypes (H1N1 and H3N2). Influenza vaccine effectiveness (VE) has varied by season, setting, and patient characteristics. Methods: Using electronic healthcare encounter data from eight US states, we evaluated influenza vaccine effectiveness (VE) against influenza-associated hospitalizations and emergency department or urgent care (ED/UC) encounters from October 2024-April 2025 among children aged 6 months-17 years and adults aged 18+ years. Using a test-negative, case-control design, we compared the odds of influenza vaccination between acute respiratory illness (ARI) encounters with a positive (cases) versus negative (controls) test for influenza by molecular assay, adjusting for confounders. Results: Analyses included 108,618 encounters (5,764 hospitalizations and 102,854 ED/UC encounters) among children and 309,483 encounters (76,072 hospitalizations and 233,411 ED/UC encounters) among adults. Among children across care settings, 17.0% (6,097/35,765) of cases versus 29.4% (21,449/72,853) of controls were vaccinated. Among adults, 28.2% (21,832/77,477) of cases versus 44.2% (102,560/232,006) of controls were vaccinated. VE was 51% (95% confidence interval [95% CI]: 41-60%) against influenza-associated hospitalizations and 54% (95% CI: 52-55%) against influenza-associated ED/UC encounters among children. VE was 43% (95% CI: 41-46%) against influenza-associated hospitalizations and 49% (95% CI: 47-50%) against influenza-associated ED/UC encounters among adults. Conclusions: Influenza vaccination provided protection against influenza-associated hospitalizations and ED/UC encounters among children and adults in the US during the severe 2024-25 influenza season. These findings support influenza vaccination as an important tool to reduce influenza-associated disease.

Background: The U.S. 2024-2025 influenza season was characterized by sustained elevated activity from November 2024 to April 2025, with circulation of both influenza A(H1N1)pdm09 and A(H3N2), the latter of which included some antigenically drifted viruses. Methods: From October 1, 2024, to April 30, 2025, a multistate respiratory virus surveillance network enrolled adults hospitalized with acute respiratory illness in 26 U.S. medical centers. Influenza vaccine effectiveness (VE) against influenza-associated hospitalization and severe in-hospital outcomes was estimated using a test-negative study. The odds of influenza vaccination among influenza-positive case patients and influenza-negative control patients were compared using multivariable logistic regression; VE was calculated as (1-adjusted odds ratio for vaccination) x 100, expressed as a percent. Results: The 2024-2025 seasonal influenza vaccine was effective against influenza-associated hospitalization (VE: 40% [95% confidence interval (CI): 32%-47%]), consistent across age group and influenza A subtypes. Influenza vaccination also reduced the overall risk of all severe in-hospital outcomes evaluated, including standard oxygen therapy (VE: 41% [95% CI: 31%-50%]), non-invasive advanced respiratory support (VE: 38% [95% CI: 19%-52%]), invasive organ support (VE: 58% [95% CI: 44%-69%]), ICU admission (VE: 58% [95% CI: 47%-67%]), and death (VE: 52% [95% CI: 18%-71%]) with effectiveness varying by influenza A subtype and age. Conclusions: Influenza vaccination reduced the risk of influenza-related hospitalization and severe in-hospital outcomes in adults during the severe 2024-2025 influenza season compared to those not vaccinated.

Background Nigeria has experienced its largest recorded diphtheria outbreak since late 2022, centred on Kano State, where facility-based surveillance documented over 25,000 confirmed cases. The true community burden remains unknown. We conducted a population-based household survey to estimate community attack rates, mortality, vaccination coverage, and determinants of infection and death. Methods We performed a retrospective household survey (September-October 2024) using spatially randomised cluster sampling (65 clusters, ~15 households each; recall period January 2023 to interview). Survey-weighted analyses, multivariable logistic regression, and sensitivity analyses were used. Findings We enrolled 7,998 individuals from 1,068 households. The community attack rate was 1.1% (95% CI 0.7-1.4), 4.2 times (2.7-5.3) higher than facility-based estimates. The case fatality ratio was 8.8% (1.9-15.6) overall and 21.3% among children under five; two thirds of deaths occurred at home. Delayed care-seeking of four or more days was associated with markedly higher mortality (risk ratio 32.6, 95% CI 2.4-450.0). Vaccination was strongly protective against death (vaccine effectiveness 57%, 95% CI 34- 72%; E-value 4.07). Among campaign-eligible children, routine EPI coverage was 56.6%; the reactive campaign reached few previously unvaccinated children (99.7% overlap with prior recipients), leaving 11.6% of eligible children unvaccinated. Interpretation Community diphtheria burden substantially exceeded facility surveillance estimates, with most deaths occurring outside the health system. Delayed care-seeking and low vaccination coverage were the main drivers of mortality, highlighting the need for improved community surveillance, decentralised care, and better-targeted vaccination.

Background. Vietnam's disease burden has shifted from communicable, maternal, neonatal, and nutritional (CMNN) causes to non-communicable diseases (NCDs), but the tempo, drivers, and regional positioning of this transition have not been jointly quantified. We characterised Vietnam's epidemiological transition 1990-2023 against ten Southeast-Asian (SEA) peers. Methods. Using Global Burden of Disease 2023 data, we computed joinpoint-regression AAPC with 95% CI (BIC-penalised, up to three break-points) for age-standardised DALY rates and cause-composition shares. We applied Das Gupta three-factor decomposition to 1990-2023 absolute DALY change (population-size, age-structure, age-specific-rate effects) and benchmarked Vietnam's NCD share against an SDI-conditional peer trajectory via leave-one-out quadratic regression. Premature mortality was quantified as WHO 30q70 under both broad NCD and strict SDG 3.4.1 definitions, using Chiang II life-table adjustment identically across all eleven countries. Findings. The CMNN age-standardised DALY rate fell from 13,295.9 to 4,022.1 per 100,000 (AAPC -4.63%/year; 95% CI -4.80 to -4.46); the NCD rate fell only from 21,688.2 to 19,282.8 (AAPC -0.37; -0.45 to -0.30). NCD share of total DALYs rose from 52.99% to 70.67% (+17.67 pp; AAPC +1.09). Vietnam ranked fourth of eleven SEA countries in 2023 (up from sixth in 1990) and sat 5.3% above the SDI-expected trajectory. Das Gupta decomposition attributed the +10.63 million NCD DALY increase to population growth (+6.26 M) and ageing (+6.08 M); rate change removed only 1.71 M. Premature NCD mortality fell from 25.02% to 21.80% (broad, 12.9% reduction) and from 22.17% to 19.50% (SDG 3.4.1, 12.0%; Vietnam sixth of eleven) - far short of the SDG 3.4 one-third-reduction target. Interpretation. Vietnam has entered a disability- and ageing-dominated NCD phase. Meeting SDG 3.4 by 2030 requires population-scale primary prevention sized to demographic momentum.

BackgroundWe explored the efficacy of AS01E-adjuvanted respiratory syncytial virus prefusion F protein-based vaccine (adjuvanted RSVPreF3) in subpopulations of participants with underlying medical conditions in the multi-country, phase 3 AReSVi-006 trial (conducted May/2021-May/2024). MethodsMedically stable [≥]60-year-olds were 1:1-randomised to receive one adjuvanted RSVPreF3 or placebo dose pre-RSV season 1. In exploratory post-hoc analyses in subgroups of participants with underlying conditions (including COPD, asthma, diabetes, obesity [BMI[≥]30 kg/m2]), we evaluated efficacy of one vaccine dose against RSV-related lower respiratory tract disease (RSV-LRTD), acute respiratory illness (RSV-ARI), and RSV-ARI-related complications (e.g., pneumonia, COPD/asthma exacerbation, cardiovascular events). We also evaluated (post-hoc) RSV-ARI-related systemic corticosteroid and antibiotics use in participants with COPD or asthma. ResultsThe efficacy analyses comprised 12,468 vaccine and 12,498 placebo recipients. Efficacy against RSV-LRTD over three RSV seasons was similar among participants with COPD (75.1%, 95% CI: 40.2-91.4), asthma (65.8%, 31.0-84.7), diabetes (69.8%, 37.5-87.1), and obesity (74.1%, 56.4-85.5) as in the overall study population (62.9%, 97.5% CI: 46.7-74.8). Efficacy was also observed against RSV-ARI in these subgroups. Efficacy against RSV-ARI-related complications was 74.4% (95% CI: 11.2-95.2) in participants with COPD and 60.8% (-9.9-88.7) in those with asthma. Among participants with COPD, 15.4% (1.9-45.4) of RSV-ARI episodes in vaccine vs 22.4% (12.5-35.3) in placebo recipients were treated with systemic corticosteroids, and 46.2% (19.2-74.9) vs 56.9% (43.2-69.8) with antibiotics. ConclusionsPost-hoc analyses of the AReSVi-006 trial suggest that adjuvanted RSVPreF3 may help prevent RSV-ARI, RSV-LRTD, and RSV-related complications in medically stable older adults with underlying medical conditions like COPD and asthma. Trial registrationClinicalTrials.gov: NCT04886596 SummaryPost-hoc analyses of the AReSVi-006 trial suggest that 1 dose of adjuvanted RSVPreF3 may help prevent RSV-related illness and complications over 3 consecutive RSV seasons in subgroups of [≥]60-year-olds with chronic medical conditions, e.g., COPD and asthma.

Context: In the UK, and in other countries, people living with a terminal illness are eligible for financial support to help with the costs of serious illness and to support their dignity and independence. This study investigates the take-up of benefits in the last year of life and identifies sociodemographic, clinical, and geographical factors associated with underclaiming. Methods: Retrospective cohort study using linked mortality, Census and benefits data for all people who died aged 16+ from chronic illnesses in England and Wales between 1 May 2018 and 30 April 2021. Outcome was receipt of non-means tested disability benefits in the last 12 months of life. We describe geographical variation in take up, and association with sociodemographic, clinical and geographical exposures using Poisson models. Findings: Our population included 1,049,493 eligible decedents, with an overall take-up rate of 65.9%. After adjusting for sociodemographic factors, variation in take-up by cause of death was wide: liver disease 44% (95% CI 43, 45%), heart failure 52% (51, 52%), cancer 62% (61, 62%), dementia 75% (74, 75%), and neurodegenerative diseases 90% (88, 91%). Across Local Authorities, the age-and-sex-standardised take-up varied from 53% to 78%; rates were generally higher in more deprived areas, but not uniformly. Conclusions: In England and Wales, 1 in 3 people who die from expected causes (120,000 each year) do not receive the benefits for which they are eligible. Our analysis uses novel data linkages and highlights clinical and sociodemographic groups and geographical areas that could be targeted with proactive take-up initiatives.

BackgroundTuberculosis (TB) and human immunodeficiency virus (HIV) are leading causes of infectious disease deaths, with disproportionate impact in low- and middle-income countries (LMICs). Despite well-established biological relationships between these diseases, there is limited information on how TB prevalence differs between people living with and without HIV. MethodsWe conducted a systematic review and meta-analysis of TB prevalence surveys conducted in LMICs and published during January 1st 1993-October 13th 2025 (PROSPERO CRD42024503853). We extracted bacteriologically-confirmed TB prevalence estimates stratified by participant HIV status. Surveys that offered HIV testing to all, sputum-collection-eligible, or TB-positive participants were included in the primary analysis. We applied Bayesian meta-regression to estimate pooled risk ratios (RR) of bacteriologically-confirmed TB prevalence among participants living with versus without HIV. Additionally, we estimated country-level and overall TB notification-to-prevalence (N:P) ratios by HIV status. FindingsOf 10,211 potentially relevant publications, 12 TB prevalence surveys--representing 264,530 participants within nine countries in Southern and Eastern Africa--were used in the primary analysis. Reported TB prevalence was higher among participants living with versus without HIV in 11/12 surveys, with an overall pooled RR of 3{middle dot}86 (95% credible interval: 2{middle dot}41-5{middle dot}53). N:P ratios were higher among participants living with HIV in all examined countries. The overall pooled N:P ratios were 1{middle dot}74 (0{middle dot}59-4{middle dot}56) and 0{middle dot}48 (0{middle dot}17-1{middle dot}20) among participants living with versus without HIV, respectively. InterpretationIn Southern and Eastern Africa, bacteriologically-confirmed TB prevalence is three- to six-times higher among people living with HIV. Comparison of prevalence and notification data suggest higher rates of TB diagnosis for people living with versus without HIV, but also indicates substantial delays in the detection of untreated TB cases for both populations. FundingWellcome Trust, UK National Institute for Health and Care Research, UK Foreign, Commonwealth and Development Office, NIH. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSThere is limited systematic evidence on how the prevalence of TB disease differs between people living with HIV and without HIV. Multiple observational cohorts have described substantially elevated TB incidence among populations with HIV, but disease prevalence will also be affected by differences in mortality and treatment uptake rates. We searched PubMed from inception through January 21, 2026 using the search string ((HIV AND TB) OR HIV/TB) AND (prevalence AND (systematic review OR meta-analysis)) without any restrictions on language. We also reviewed investigators personal libraries. This search yielded 506 publications; however few of these included prevalence data. An analysis conducted in 2020 synthesized HIV status-stratified data from seven national TB prevalence surveys in Africa and found that HIV prevalence was lower among prevalent TB cases than among notified cases. This study did not include subnational surveys and did not distinguish between survey participants with self-reported or test-confirmed HIV status. Added value of this studyThis study synthesized TB prevalence data, stratified by participant HIV status, from national and subnational surveys conducted in LMICs and published between January 1st 1993 and October 13th, 2025. Collated data represented 681,402 survey participants across ten countries. All but one study were conducted in Southern and Eastern Africa. We limited our primary analysis to surveys that systematically tested participants for HIV and bacteriologically-confirmed TB. The prevalence of bacteriologically-confirmed TB was estimated to be three to six times higher than among people living with versus without HIV. Ratios of TB notifications to TB prevalence were higher for people living with HIV compared to people without HIV, suggesting higher rates of TB case detection (and likely shorter duration of disease) for people living with HIV and untreated TB than those without HIV. Implications of all available evidenceFew estimates of community-representative TB prevalence stratified by participant HIV status exist. These surveys have been concentrated in Southern and Eastern Africa, despite TB-HIV burden being distributed globally. Our findings highlight the elevated burden of TB among people living with HIV in these settings, as well as the limited data on the intersection of TB and HIV epidemiology in other world regions. Furthermore, our comparison of notification and prevalence data demonstrate substantial shortfalls in TB case detection, regardless of an individuals HIV status.

Background: Oseltamivir is an antiviral medication for influenza that can reduce the duration of symptoms and may lower the risk of some complications. Recommendations for use of oseltamivir include in the outpatient setting for individuals at higher risk of developing influenza complications. Objectives: To describe oseltamivir initiation and treatment completion among influenza-positive outpatients and identify factors associated with each. Methods: In a U.S. outpatient household transmission study, index participants with laboratory-confirmed influenza provided up to 12 days of detailed information on medication use. We described oseltamivir initiation among index cases and treatment course completion of [&ge;] 10 doses among cases who initiated oseltamivir. We used unadjusted and adjusted logistic regression to identify factors associated with initiation and course completion. Results: Among 823 enrolled index cases, 324 (39%) initiated oseltamivir treatment. Of 406 persons at higher risk for influenza complications, 172 (42%) initiated treatment. Oseltamivir initiation was lowest among children aged 2 to < 5 years (19%) compared to all other age groups. Among 313 cases who initiated oseltamivir, 42% completed the recommended treatment course of [&ge;] 10 doses. Among 163 individuals at higher risk of influenza complications, 69 (42%) completed the recommended treatment course of [&ge;] 10 doses. Children < 2 years were significantly less likely to complete treatment compared to adults aged 18-50 years (aOR: 0.21, 95% CI: 0.04, 0.78, p= 0.030); reasons for discontinuation could not be determined. Conclusions: These findings reveal differences in oseltamivir treatment in an outpatient setting among groups at higher risk for influenza complications.

BackgroundIn chronic asymptomatic Plasmodium vivax infections, the spleen accounts for more than 98% of total-body parasite biomass. Whether this splenic tropism also exists in acute infection and how the spleen influences pathogenesis have not been systematically explored. Materials and MethodsIn Papua, Indonesia, we compared plasma levels of P. vivax lactate dehydrogenase [PvLDH]) and circulating parasitemia in 24 spleen-intact and 25 previously splenectomized patients with acute uncomplicated vivax malaria. Clinical and hematology data were collected and plasma markers of intravascular hemolysis (cell-free hemoglobin [CFHb]), endothelial activation (angiopoietin-2), inflammation (interleukin [IL]-1 beta, IL-6, IL-18, IL-10, tumor necrosis factor-alpha) and neutrophil activation (elastase) were measured by ELISA. Giemsa-based histology in one spleen from an untreated patient splenectomized for trauma during an episode of acute vivax malaria enabled direct assessment of splenic and circulating parasitemia and biomass microscopically. ResultsCirculating parasitemia was 4-times higher in splenectomized compared to spleen-intact patients (median 21,100 vs 4,820 parasites/{micro}L, p=0.0002) but total-body P. vivax biomass (PvLDH) was 3-times lower in patients without a spleen (median 721 vs 2,140 ng/mL, p=0.026). Parasite staging and greater organ-specific symptoms suggest redistribution of parasites in the absence of a spleen. Linear regression modeling, adjusting for circulating parasitemia, patient age, sex and duration of fever, demonstrated an 8.1-fold higher PvLDH concentration in spleen-intact patients (95% confidence interval [CI]: 3.4-19.5-fold, p<0.0001), indicating a splenic biomass accounting for 89% (95%CI: 77.3-95.1%) of total-body parasites. Histopathology revealed a spleen-to-blood biomass ratio of 10.7, in-line with the PvLDH-based estimate. In spleen-intact patients, splenic P. vivax biomass correlated strongly with markers of disease intensity, endothelial activation and systemic inflammation, whereas circulating parasitemia correlated weakly or not at all. Compared to spleen-intact patients, CFHb, endothelial activation and systemic inflammation were higher in splenectomized patients while inflammasome-dependent responses were lower. ConclusionsP. vivax is predominantly an infection of the spleen, even in acute clinical vivax malaria. We conservatively estimate that 89% of total-body parasite biomass in acute infection is splenic. While the size of this hidden population correlates with disease intensity, the spleen likely regulates inflammatory pathways and heme-associated pathology.

Background: Several large multisite studies have been conducted to describe etiology-specific burden of diarrhea among children in low-resource settings. Here, we combined data across studies to describe geographic and temporal trends in incidence and attributable fractions (AFs) of etiology-specific moderate-to-severe diarrhea (MSD), and to evaluate etiology-specific case fatality ratios (CFRs). Methods: We harmonized case definitions and analytic methods across the Global Enteric Multicenter Study (GEMS), Malnutrition and Enteric Disease (MAL-ED), Vaccine Impact on Diarrhea in Africa (VIDA), AntiBiotics for Children with severe Diarrhea (ABCD), and Enterics for Global Health (EFGH) studies. Cases were 6-35-month-olds with acute MSD. Incidence estimates for GEMS, VIDA, and EFGH were adjusted for enrollment, healthcare seeking, and diagnostic testing. AFs were calculated as the proportion of MSD cases attributed to each etiology, and CFRs were estimated within 14 and 90 days of an MSD episode. Findings: Pre-rotavirus vaccine introduction, rotavirus had the highest incidence and was the leading etiology among 6-11-month-olds, accounting for approximately 22-28% of MSD; the proportion of diarrhea due to rotavirus declined following vaccine introduction, with average AF 10-11% in Africa and Asia. Shigella incidence was highest among 12-23-month-olds and was the dominant etiology among 12-23 and 24-35-month-olds, causing approximately one-third to one-half of MSD. Overall, 90-day mortality declined substantially over time, from 2.21% in GEMS to 0.30% in EFGH. Bacterial (2.52%) and protozoal pathogens (3.55%) had higher average CFRs than viral pathogens (1.42%). Conclusion: Harmonized analysis of five multisite studies reveals consistent evidence that rotavirus and Shigella are the dominant causes of MSD in children under three years in low-resource settings, with burden shifting toward Shigella following rotavirus vaccine introduction.

Background During Nigeria's largest recorded diphtheria outbreak, hospital capacity in Kano State was rapidly overwhelmed. Medecins Sans Frontieres introduced home-based care (HBC) for patients with mild disease to prioritise facility-based care for severe cases. We assessed whether HBC was non-inferior to facility-based treatment in terms of mortality, sequelae, and household transmission. Methods We conducted a retrospective matched cohort study. Mild diphtheria cases treated between January 2023 and May 2024 were matched 1:1 by treatment modality (HBC or diphtheria treatment centre [DTC]) on sex, age group, vaccination status, and residence. Conditional logistic regression estimated the association between treatment modality and mortality, with robustness assessed through propensity score weighting, sensitivity analyses, and E-value computation. Findings Of 990 sampled patients, 678 (367 HBC, 311 DTC) were enrolled (68.5%). After adjustment, treatment modality was not independently associated with mortality (HBC vs. DTC: aOR 0.40, 95% CI 0.13-1.30), with similar estimates across sensitivity analyses (E-value 4.40). Clinical complications were the strongest predictor of death (aOR 23.1, 95% CI 1.73-307). Vaccination was protective (aOR 0.28, 95% CI 0.08-0.94) and treatment delay of four or more days increased mortality (aOR 4.15, 95% CI 1.23-14.0). HBC was not associated with increased household transmission or long-term sequelae. Interpretation Vaccination and early treatment, rather than care setting, were the main determinants of survival. When supported by clinical triage and structured follow-up, decentralised care can be used to manage mild cases during diphtheria epidemics in settings with constrained hospital capacity.

Background: Ribavirin is a guanosine analogue with clinical antiviral activity against a range of RNA viruses including hepatitis C virus (HCV), respiratory syncytial virus and Lassa virus. Several potential mechanisms of action have been proposed, but there is limited data supporting them clinically. Methods: We studied 196 HCV-infected participants from a trial of short-course directly antiviral therapy (STOPHCV-1) which included a factorial randomisation to ribavirin versus no ribavirin. Deep sequencing of the HCV genome was performed on samples with detectable viremia from three time-points: baseline (n = 191), day 3 of treatment (n = 25) and post-treatment failure (n = 47). Results: Ribavirin exposure significantly increased total mutational load at treatment failure (P = 0.0065) and enriched classical ribavirin-associated transitions, including G->A (P = 0.026) and C[-&gt;]U (P = 0.004), along with other key changes including A->G (P = 0.005), U->C (P = 0.023), C->G (P = 0.010), and U->A (P = 0.026). The resulting mutational signature was broad, not dominated by G-related changes. Region-specific analyses demonstrated this increase was broadly distributed across the viral genome, without strong evidence for protection of specific regions. Non-synonymous to synonymous mutation ratios (dN/dS) rose at day 3 (P = 5.5e-5) before declining at failure (P = 8.5e-7), with trends toward higher dN/dS in the ribavirin group at day 3 (P = 0.06). Conclusions: Ribavirin acts as a potent in vivo mutagen, driving viral populations toward genome-wide diversity rather than selecting a few highly fit drug-resistant clones. These findings support an error-catastrophe model.

Background Post-licensure vaccine effectiveness and impact studies provide evidence on how vaccines perform under routine programme conditions in the real world. In sub-Saharan Africa (SSA), vaccine introductions frequently coincide with concurrent public health and social measures that may influence disease risk and transmission. Failure to account for these concurrent interventions may affect the interpretation of vaccine effects. Methods We conducted a systematic review of post-licensure vaccine effectiveness and impact studies conducted in children under five years of age in SSA. Electronic databases were searched for peer-reviewed studies published between January 2000 and December 2019. Eligible studies used observational designs to estimate vaccine effectiveness or population-level impact. Two reviewers independently screened studies, extracted data, and assessed methodological quality using Joanna Briggs Institute tools. We examined study designs, vaccines evaluated, outcomes assessed, and whether public health and social measures (PHSMs) were measured or adjusted for. A narrative synthesis was undertaken. In addition, we conducted a meta-analysis for rotavirus and pneumococcal conjugate vaccines where we explored the heterogeneity in individual-level effectiveness estimates where designs and outcomes were comparable. Results Sixty-four studies met the inclusion criteria, covering eight vaccine-preventable diseases. Rotavirus vaccines were most frequently evaluated, followed by pneumococcal conjugate vaccines. Case-control and ecological designs were most common, while cohort and time-series analyses were less frequently used. None of the included studies collected, reported, or adjusted for PHSMs such as nutrition, WASH, or access to healthcare. The implications of this omission varied by pathogen. Rotavirus vaccine effectiveness estimates from comparable individual-level designs were consistent across settings, with no evidence of between-study heterogeneity. Pneumococcal vaccine effectiveness estimates showed substantial heterogeneity, which appeared to reflect differences in outcome definitions, host risk profiles, and study context. Estimates for other vaccines were generally protective in direction, although the magnitude and precision varied across studies. Conclusions Post-licensure vaccine effectiveness and impact studies in SSA rarely account for concurrent PHSMs. The consequences of this omission are not uniform across vaccines. For some pathogens, effectiveness estimates appear robust to unmeasured contextual change, while for others they are highly sensitive to outcome choice and setting. Future evaluations should prioritise systematic measurement of key PHSMs and consider study designs that better account for time-varying context. Strengthening routine data systems to capture these factors is essential for generating interpretable evidence to inform immunisation policy.

Background: Patient matching in intensive care databases yields sample sizes too small for individualised outcome analysis. Current AI systems provide population-level guideline summaries but omit stratification variables that may invert therapy signals at the individual level. Methods: We developed the Therapeutic Distance framework, which computes the z-standardised distance between a patient's clinical parameters and the centroid of MIMIC-IV patients who received each therapy: d(P,T) = sum of wi(T) x |(Li - mui(T)) / sigmai|. We hypothesise that patients at the same distance to a therapy (same orbit) have comparable outcomes. Six validation experiments were performed on 11,627 sepsis patients (SAPS-II 30-80) from MIMIC-IV v3.1. Results: Echo-stratified vasopressin recipients showed mortality of 30.1% (n=146, 95% CI 22.6-37.7%) versus 53.9% without echo (n=2,426, 95% CI 51.9-55.9%). Confidence intervals did not overlap (bootstrap, 1,000 resamples). However, echo-stratified patients had lower general severity (SAPS-II 49.2 vs 53.9) but higher cardiac biomarkers (troponin 1.0 vs 0.51 ng/mL), indicating that the observed difference is compatible with both severity confounding and a possible cardiac-specific vasopressin effect. Leave-one-out prediction with uniform weights achieved AUC 0.61 as a structural baseline. Conclusions: Therapeutic Distance replaces patient matching with orbit matching, substantially increasing usable sample sizes. The echo-vasopressin finding is hypothesis-generating and mechanistically plausible but not causally proven. The framework is intended as a clinical decision support signal under uncertainty, not as a causal inference method.

Rationale: Sepsis is a life-threatening syndrome causing significant morbidity and mortality especially in the aging population. Clonal hematopoiesis of indeterminate potential (CHIP) is an age-related condition of clonal expansion of hematopoietic stem cells harboring somatic mutations associated with increased incidence of chronic illness and all-cause mortality. Objective: Evaluate the association of pre-illness CHIP with mortality and morbidity in patients admitted to the ICU with sepsis. Methods: We performed a retrospective study using a de-identified electronic health record linked with a DNA biorepository. We identified adult patients with sepsis who had DNA collected prior to ICU admission. We tested the association between CHIP status, determined from whole-genome sequencing, and ICU mortality, organ support-free days, and long-term survival adjusting for age, sex, race and Sequential Organ Failure Assessment (SOFA) score on ICU admission. Measurements and Main Results: Pre-illness CHIP was associated with increased sepsis mortality (OR = 1.54, 95% CI 1.13 to 2.07, P = 0.005) and fewer days alive and free of organ support (-1.7 days, 95% CI -3.2 to -0.2, P = 0.028) after adjusting for age, sex, race, and SOFA score. In sepsis survivors, CHIP was also associated with increased long-term mortality after discharge (HR 1.40, 95% CI 1.01 to 1.93, P = 0.041). Conclusions: Pre-illness CHIP was independently associated with increased mortality and morbidity in critically-ill adults with sepsis. These findings suggest that CHIP is a risk factor for sepsis severity. Elucidating the mechanism underlying this association could uncover new therapeutic interventions for sepsis.

Background Six years after its emergence, SARS-CoV-2 continues to have a substantial burden. The impact of vaccination and the optimal timing of its rollout remain uncertain given existing population immunity and variability in outbreak timing between summer and winter. Methods The US Scenario Modeling Hub convened its 19th round of ensemble projections for COVID-19 hospitalizations and deaths in the United States, where eight teams projected trajectories in each US state and nationally from April 2025 to April 2026 under five scenarios regarding vaccine recommendations and timing. Recommendations had two eligibility scenarios (high-risk individuals only and all-eligible) and two timing scenarios (classic start: mid-August, earlier start: late June). These were crossed to create four scenarios and were compared against a counterfactual scenario with no vaccination. Findings Compared to no vaccination, our ensemble projections estimated 90,000 (95% PI 53,000-126,000) hospitalizations averted in the high-risk and classic timing scenario across the US. Expanding to all-eligible age-groups averted an additional 26,000 (95% PI 14,000-39,000) hospitalizations, which when coupled with the early vaccination timing, was projected to further reduce national hospitalizations by 15,000 (95% PI -3,000-33,000). The majority of teams projected both summer and winter waves. Implications We project COVID-19 will cause significant hospitalizations and deaths in the US in the 2025-26 season and estimate significant benefits from a broad all-eligible vaccination recommendation. The results also suggest an additional benefit is likely to be gained from an earlier vaccination campaign. Funding Centers for Disease Control and Prevention; National Institute of Health (US), National Science Foundation (US)

Background: Although the hemagglutination inhibition (HAI) titer remains the gold standard correlate of protection against influenza, it does not fully capture the broader antibody responses that contribute to immunity. Methods: We analyzed immune responses in paired pre-infection and convalescent sera from 306 RT-PCR-confirmed A/H3N2 infections from two household studies (2014-18) in Managua, Nicaragua. Antibody responses were measured by HAI and enzyme-linked immunosorbent assays (ELISAs) against full-length hemagglutinin (HA), the HA stalk, and neuraminidase (NA). Participants were classified as HAI responders ([&ge;]4-fold HAI rise), alternate responders (no HAI rise but [&ge;]4-fold boost in [&ge;]1 ELISA), or no-response individuals (no [&ge;]4-fold rise in any assay). We compared demographic, clinical, and pre-infection antibody characteristics across these groups. We also analyzed predictors of an NA response. Results: Overall, 77% of participants had HAI seroconversion or a 4-fold rise. Among the 23% HAI non-responders, 62% had alternate antibody responses. No-response individuals had the highest pre-infection HAI and full-length HA titers (p < 0.0001), the lowest viral loads, and the fewest fever or influenza like illness (ILI) symptoms (p < 0.01). An NA response was more common among symptomatic individuals (p = 0.0483) and those with low or high baseline NA titers. Conclusions: High baseline HAI titers can limit detectable 4-fold rises and are associated with milder illness. Evaluating additional immune responses may capture a more complete picture of the host response to infection, thereby improving surveillance and informing vaccine development. Keywords: Influenza A/H3N2; Hemagglutination inhibition (HAI); Neuraminidase antibodies; symptomatic vs asymptomatic infection; correlates of protection.

Background: Partial resistance to artemisinins (ART-R) has emerged in East Africa, associated with mutations in the Plasmodium falciparum kelch13 gene. It is currently unclear whether ART-R has implications for gametocyte production or for onward transmission to mosquitoes. Methods: In a cohort of uncomplicated malaria patients attending Kalongo Hospital in northern Uganda, we quantified carriage of PfKelch13 mutant parasites by conventional sequencing and droplet digital PCR (ddPCR) for the C469Y and A675V mutations. Prevalence and density of gametocytes and ring-stage parasites were assessed by microscopy and quantitative reverse-transcriptase PCR (qRT-PCR). Lumefantrine concentrations, indicative of prior malaria treatment, were determined by ultra-high performance liquid chromatography-tandem mass spectrometry. Transmission potential of wild-type and PfKelch13 mutant parasites was assessed by mosquito feeding assays and complemented with molecular characterization of parasites in wild-caught mosquitoes from household resting catches. Findings: We enrolled 235 patients with symptomatic P. falciparum infection; PfKelch13 C469Y or A675V mutations were detected in 35.8% (78/218) of infections by sequencing and 59.1% (136/230) by ddPCR. Gametocyte carriage was 24.0% (56/233) by microscopy and 56.6% (133/235) by qRT-PCR and not associated with the abundance of PfKelch13 mutant parasites by ddPCR (p=0.603). Among a total of 227 mosquito feeds with patient whole blood, 1.4% (120/8745) of mosquitoes became infected. Mosquito infection rates were positively associated with gametocyte density ({beta} = 0.39, 95% CI = 0.23-0.59, p < 0.001) without an observed interaction with the abundance of PfKelch13 mutant parasites (p = 0.452). PfKelch13 C469Y or A675V mutations were detected in 40.1% (21/52) of malaria-infected bloodmeals of field-caught mosquitoes and in 28.0% (7/25) of sporozoite-positive mosquitoes. Interpretation: We conclude that pfkelch13 mutations are very common in patients in northern Uganda with uncomplicated malaria, mostly in multiclonal infections. We observed no evidence that ART-R affected gametocyte production or transmission to mosquitoes. Funding: Dutch Research Council (NWO)