influenza vaccine

Overview

The influenza vaccine is a preventive biological therapy designed to elicit protective immunity against influenza virus infection by stimulating the production of antibodies targeting viral surface antigens, most prominently hemagglutinin (HA). Multiple formulations exist to address the diverse needs of different populations: standard-dose inactivated influenza vaccines (IIV), high-dose formulations for older adults, live-attenuated influenza vaccines (LAIV) administered intranasally, and recombinant protein-based vaccines. Pediatric formulations for children aged 6–35 months are typically low-dose (0.25 mL, 7.5 μg hemagglutinin per strain), whereas older children and adults receive higher antigen concentrations. Because influenza viruses undergo continuous antigenic evolution, the composition of seasonal influenza vaccines is updated annually to match circulating strains, and vaccination timing relative to the influenza season is a critical determinant of individual and population-level protection.

Beyond their core immunological function, influenza vaccines occupy an important position in public health strategy, particularly for high-risk groups including older adults, young infants, immunocompromised individuals, and those receiving immunosuppressive Targeted therapies such as rituximab or immune checkpoint inhibitors (ICIs). The absence of approved influenza vaccines for young infants and the persistent challenge of achieving broad, durable immunity underscore ongoing efforts to develop universal or next-generation formulations, including HA stem-targeting nanoparticle vaccines and adjuvanted platforms intended to broaden cross-strain protection.

Focus of Latest Publications

Recent publications on influenza vaccine have focused on both clinical effectiveness and the behavioral and implementation factors that influence uptake. Several studies evaluated vaccine effectiveness in pediatric populations, including primary care settings in the European Union and European Economic Area, as well as influenza-associated hospitalization and outpatient visits across multiple seasons. Another pediatric study examined influenza vaccination effectiveness against hospitalization and the effects of repeated annual vaccination, reflecting ongoing interest in how prior vaccination history may modify protection. In Brazil, a nationwide retrospective cohort study of hospitalized, RT-PCR-confirmed influenza cases also identified influenza vaccination as a protective factor against mortality, alongside oseltamivir use, in a large surveillance dataset.

A separate line of research has examined influenza vaccine hesitancy and acceptance. Among pediatric healthcare workers in China, social media trust and exposure were associated with influenza vaccine hesitancy, with confidence in vaccines mediating a substantial portion of the relationship. A cross-sectional survey in seven Chinese megacities also assessed the prevalence and determinants of influenza vaccine hesitancy versus uptake in urban populations. In healthcare workers, another study used a discrete choice experiment to explore whether introducing enhanced influenza vaccines could influence vaccination coverage, indicating interest in how vaccine attributes may affect acceptance.

Safety and delivery of influenza vaccination have also been studied in specific populations. In Canadian children and adolescents with autoimmune and/or immunocompromised conditions, active surveillance from the CANVAS network found that co-administered COVID-19 and influenza vaccination was not associated with an increased risk of short-term health events, although influenza-only subgroups were underpowered. A separate pediatric inpatient study examined the impact of the COVID-19 pandemic on hospital-based delivery of influenza vaccines and other routine immunizations, highlighting disruptions in vaccine administration during the pandemic period.

Public health and economic evaluations have further addressed the role of influenza vaccine in older adults and high-risk groups. One study assessed the burden of influenza and the cost-effectiveness of introducing a seasonal influenza vaccination programme among adults aged 60 years and older in India, where publicly funded seasonal influenza immunization is not yet established. Together, these publications emphasize influenza vaccine as a tool for reducing severe outcomes, a target for improving uptake through communication and vaccine design, and an intervention whose delivery and safety remain important across age groups and clinical settings.

Key Publications

• NEWJun Association between COVID-19 booster vaccination and influenza mortality: a nationwide retrospective cohort study using the SIVEP-Gripe database in Brazil. (Immunologic research, 2026, PMID 42324378): "Protective factors included influenza vaccination (OR 0.77) and oseltamivir use (OR 0.81)."
• May Impact of social media use on influenza vaccine hesitancy among pediatric healthcare workers: The mediating role of 3Cs. (Human vaccines & immunotherapeutics, 2026, PMID 42127305): "This study aimed to examine whether confidence, complacency, and convenience (3Cs) mediate the association between social media use and influenza vaccine hesitancy."
• Jun Impact of the COVID-19 Pandemic on National Pediatric Inpatient Vaccine Delivery. (Hospital pediatrics, 2026, PMID 42128415): "...impact on national inpatient pediatric vaccine delivery rates for...influenza vaccines (IIVs)..."
• May Influenza vaccine hesitancy versus uptake in seven Chinese megacities: a cross-sectional survey. (Infectious diseases of poverty, 2026, PMID 42071229): "This study aimed to assess the prevalence and determinants of influenza vaccine hesitancy (IVH) among urban populations to inform strategies for improving vaccine uptake in China."
• May Burden of Influenza and Cost-Effectiveness Analysis of Introduction of an Influenza Vaccination Programme Among Older Adults in India. (Influenza and other respiratory viruses, 2026, PMID 42062199): "We estimate the cost-effectiveness and budgetary impact of introducing seasonal influenza vaccination among adults aged ≥60 years in India, a known high-risk group."
• Apr Safety of COVID-19 and influenza vaccines in children and adolescents with immunocompromised or autoimmune conditions: Findings from the Canadian National Vaccine Safety (CANVAS) network. (Human vaccines & immunotherapeutics, 2026, PMID 42053343): "Participants were vaccinated with COVID-19 only, seasonal influenza vaccine only, or had both vaccines co-administered and reported new or worsening health events within 7 d post-vaccination; unvaccinated participants reported new or worsening events in the prior week."
• May Attitudes towards a potential future norovirus vaccine in a representative survey of U.S. adults, February 2025. (Vaccine, 2026, PMID 41950848): "Norovirus vaccine acceptance for was similar to COVID and RSV vaccines, and slightly lower than a flu vaccine."
• May Influenza Vaccine Effectiveness in European Primary Care Pediatric Practices: 2022-2024. (Pediatrics, 2026, PMID 41936398): "To estimate influenza vaccine effectiveness (VE) in the pediatric population (<18 years) attending primary care in the European Union and European Economic Area in 2022/2023 and 2023/2024."
• May Pediatric Vaccine Effectiveness Against Influenza Hospitalization and Outpatient Visits: 2021-2024. (Pediatrics, 2026, PMID 41936402): "Understanding the protection from influenza vaccines could help inform vaccine counseling, which might improve pediatric influenza vaccination uptake."
• May Normalising enhanced influenza vaccines as a strategy to promote vaccination uptake in healthcare workers: Insights from a discrete choice experiment. (Vaccine, 2026, PMID 41921480): "the rollout of different influenza vaccines in Hong Kong."