New England Journal of Medicine

BackgroundThe SARS-CoV-2 LP.8.1 subvariant was incorporated into the 2025-2026 U.S. COVID-19 vaccines (mRNA-1273.251 and mRNA-1283.251). We evaluated immunogenicity and safety of these vaccines against vaccine-matched and emerging variants in individuals aged [≥]65 and those aged 12-64 years at high-risk of severe COVID-19. MethodsData were generated from: (1) two independent, ongoing, phase 3b/4, open-label, single-arm studies in which participants received a single dose of 50-{micro}g mRNA...

This exploratory analysis of PAX LC, a Phase 2, 1:1 randomized, double-blind, superiority, placebo-controlled trial examined whether treatment with nirmatrelvir/ritonavir (NMV/r) versus placebo/ritonavir (PBO/r) in individuals with Long COVID could reveal immune features associated with symptom improvement. Eighty-two participants (n=45 PBO/r; n=37 NMV/r) provided blood samples at baseline (Day 0) and post-treatment (Day 28). Baseline demographic and immunological phenotypes were similar in the ...

BackgroundInterleukin-6 (IL-6) is a cytokine that plays a key role in systemic hyperinflammation and may mediate the relationship between acute COVID-19 and severe long-term outcomes such as Long COVID or death. IL-6 modulating drugs may reduce patients risk of severe post-COVID-19 outcomes. MethodsWe conducted an emulated target trial in a retrospective cohort of patients with moderate-to-severe rheumatoid arthritis who were prescribed IL-6 receptor antagonists (sarilumab or tocilizumab, poole...

BackgroundSerotype 3 (S3) has remained a major cause of invasive pneumococcal disease (IPD) despite its inclusion in 13-valent pneumococcal conjugate vaccine (PCV). In October 2023, a 15-valent PCV (PCV15) including S3 was introduced into the Catalan universal childhood immunization program. MethodsWe conducted a retrospective pre-post surveillance study to compare pediatric IPD incidence in Catalonia during a pre-PCV15 period (October 1, 2022-September 30, 2023) and two post-PCV15 periods (Oct...

ImportanceRecent reports have highlighted an intense influenza activity related to the circulation of the influenza A(H3N2) subclade k variant. There is no data available on the impact of the emergence of H3N2 subclade k on the severity of the 2025-2026 epidemic or on the clinical phenotype of patients requiring admission to the intensive care unit (ICU). ObjectiveTo compare the clinical presentation, hospital mortality and virological characteristics of patients with laboratory-confirmed influ...

The prospective design of vaccine efficacy trials for deployment in outbreaks requires advance consideration of plausible outbreak scenarios, anticipated vaccine characteristics, and logistical and ethical constraints. As part of CEPIs 100 Days Mission to accelerate vaccine development against a novel Disease X, we evaluated trial designs for a hypothetical Nipah-X outbreak. We assumed Nipah-X would share key features with Nipah, including high case fatality rates and substantial super-spreading...

Since the cessation of real-time monitoring of COVID-19 hospitalizations in early 2024, the burden of and vaccine effectiveness (VE) against severe COVID-19 in the Netherlands was largely unknown. Recently, hospitalization data from 2024 were made available for the purpose of monitoring and evaluating the COVID-19 vaccination campaigns. These data were linked to the population registry, vaccination registry and healthcare use data (for classification into medical risk groups). We analyzed the n...

A number of vaccines and long-acting monoclonal antibodies have been shown to be effective in the prevention of respiratory syncytial virus (RSV) disease. However, an immune correlate of protection for RSV has not yet been identified. We conducted a systematic review to identify published reports of immunogenicity and/or efficacy in vaccines and long-acting monoclonal antibodies against RSV and performed a meta-analysis on extracted data to identify any relationship between antibody increase and...

AO_SCPLOWBSTRACTC_SCPLOWInfluenza A subclade K viruses caused high infection rates in the 2025/2026 Northern Hemisphere season, raising concerns about antigenic drift and reduced vaccine effectiveness. We measured antibody responses in matched human pre- and post-vaccination sera against a vaccine-like as well as subclade K isolates. Pre-existing immunity to subclade K variants was noted with seasonal influenza vaccination boosting titers two-fold against subclade K and three-fold against the va...

Introduction: Neurodegenerative diseases (NDDs) including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and non-AD dementias share chronic neuroinflammatory mechanisms that contribute to neuronal injury and disease progression. While anti-inflammatory therapies (AITs) are associated with reduced neurodegenerative disease risk, knowledge regarding the impact of biological sex and treatment duration across multiple NDDs remains li...

BackgroundThere is a need for synthetic peptide-based serologic assays that exploit avidity to replace whole antigens while enabling low-cost diagnostics in resource-limited settings. ObjectiveTo evaluate the diagnostic accuracy of a polymeric peptide-based ELISA leveraging avidity to enhance signal. MethodA 15-member SARS-CoV-2 peptide library corresponding to multiple epitope clusters and proteins was screened by indirect ELISA using pooled sera from RT-PCR-confirmed COVID-19 patients to ide...

COVID-19 remains a substantial public health challenge in the Netherlands. Next-generation COVID-19 vaccine, mRNA-1283, is approved in the European Union, with potential for higher relative vaccine efficacy compared with originally-licensed COVID-19 vaccines. Its potential public health and economic impact, in adults [≥]60 years and high-risk 18-59 years, was modelled versus no vaccination and originally-licensed mRNA-1273 and BNT162b2, adapting a published static Markov model with 1-year tim...

BACKGROUND AND OBJECTIVESSeasonal influenza vaccination has been shown to reduce the risk of influenza and severe complications among children 6 months and older. Since 2010, reported numbers of influenza-associated pediatric deaths among children aged <18 years have ranged from 37 during the 2011-2012 season to 289 during 2024-2025. We estimated influenza vaccine effectiveness (VE) against pediatric death from 2016-2017 through 2024-2025. METHODSWe conducted a case-cohort analysis comparing cu...

BackgroundInitial reports from the Netherlands indicate a decline in routine childhood vaccination uptake during and after the COVID-19 pandemic, with emerging evidence of reduced parental vaccine confidence. This study aimed to evaluate the long-term impact of the COVID-19 pandemic on routine childhood vaccination uptake. MethodsWe conducted a retrospective nationwide cohort study including all children born in the Netherlands in 2016-2024. First-dose DTaP-IPV vaccination status by age six mon...

Immune imprinting, also known as immune history, is a core aspect of adaptive immunity that influences antibody responses to future antigen exposures. Nevertheless, the impact of sequential flavivirus vaccinations on epitope targeting and antibody activity in humans remains incompletely understood. This question is particularly important in regions where the inactivated Japanese encephalitis virus (JEV) vaccines and the live-attenuated dengue virus (DENV) vaccines are used, as both have been ass...

An H3N2 variant, named subclade K, continues to circulate widely during the 2025-2026 influenza season. This virus possesses a hemagglutinin (HA) protein that has eleven substitutions relative to the HA of the Northern Hemisphere 2025-2026 H3N2 vaccine strain. Many of these substitutions are in epitopes in well-characterized HA antigenic sites. Despite this, interim vaccine effectiveness studies indicate that the 2025-2026 influenza vaccine provides moderate protection against H3N2 subclade K in...

Dengue virus (DENV), comprising four distinct serotypes (DENV-1 to DENV-4), poses a major public health challenge in tropical regions. Infection with one serotype confers long-term immunity to that serotype alone, while subsequent heterologous infections are associated with increased risk of severe disease, necessitating vaccines that induce durable, balanced immunity across all serotypes. However, achieving such balance immunity remains a central challenge for dengue vaccine development. Using ...

Incidence patterns of post-acute sequelae, characterised by persistence or delayed onset after the acute phase of an infection, are not well documented after infectious disease outbreaks. Nipah virus was first detected in the 1998-1999 Malaysia outbreak and remains a significant public health concern due to its high epidemic potential and recurrent outbreaks in South Asia. We conducted a systematic review on the prevalence, incidence, duration, and characteristics of post-acute sequelae in survi...

BackgroundHospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP), particularly those caused by multi-drug resistant organisms (MDROs), often require newer antibiotic treatment. The efficacy and safety of newer antibiotics compared to generic antibiotics in randomized controlled trials (RCTs) have not been evaluated before. MethodsIn this systematic review, we searched RCTs in the United States National Library of Medicine (PubMed), Cochrane Central Reg...

IntroductionSporadic colorectal cancer (CRC) remains a significant driver of worldwide morbidity and mortality. Environmental factors associated with CRC are increasingly well-described and now include generalized colonic dysbiosis and individual enteric bacteria. Clostridioides difficile is one such species, with recent mouse model work suggesting prolonged exposure to C. difficile toxin B is conducive to colonic tumorigenesis. However, there is a dearth of real-world human evidence linking C. ...