Eurosurveillance - Volume 31, Issue 13, 02 April 2026

Influenza infection is a recognised trigger of acute myocardial infarction (AMI) and stroke, but whether influenza vaccination modifies this risk remains unclear.

We aimed to quantify the short-term cardiovascular risk after laboratory-confirmed influenza infection and assess whether vaccination attenuates it.

We conducted a nationwide self-controlled case series study using Danish health registries (2014–2025) and included individuals aged ≥ 40 years with a first-ever hospital admission for AMI or stroke within ± 365 days of a PCR-confirmed influenza infection. We defined days 1–7 after specimen date as the risk period and excluded a 14-day pre-exposure period to reduce reverse causality, where influenza testing might be prompted by cardiovascular disease symptoms. We linked testing, hospitalisation, vaccination and mortality data deterministically via unique personal identifiers. We estimated incidence rate ratios (IRRs) and 95% confidence intervals (CI) with conditional Poisson regression.

Among 1,221 individuals with a first-ever AMI (n = 429; 35%) or stroke (n = 792; 65%), median age was 75 years (interquartile range: 66–82); 561 (46%) were female. After calendar-month adjustment, the IRR for cardiovascular events during the risk period was 3.5 (95% CI: 2.6–4.7), higher for AMI (IRR = 4.7; 95% CI: 3.1–7.4) than stroke (IRR = 2.9; 95% CI: 2.0–4.2). Prior influenza vaccination during the same influenza season, recorded in 610 (50%) episodes, reduced the excess risk of AMI or stroke associated with influenza infection (interaction p = 0.020).

Influenza infection conferred a transiently increased risk of first-time AMI and stroke. Vaccination substantially attenuated this risk, supporting its role in preventing cardiovascular complications after breakthrough infection.

Many countries use school-based vaccination for adolescent vaccination; it has been shown to reduce inequities in uptake compared with other delivery routes. In England, coverage for human papillomavirus (HPV), meningococcal groups A, C, W and Y (MenACWY) and tetanus, diphtheria and inactivated polio virus (Td/IPV) vaccine programmes exceeded 80% before the COVID-19 pandemic. However, recent data show declining uptake.

This study examined the relationship between socio-economic deprivation and coverage over time.

We conducted an ecological analysis of first-dose coverage for HPV (females and males), MenACWY and TdIPV in adolescents across 150 local authorities in England from 2017 to 2024. Coverage data were linked to 2025 Index of Multiple Deprivation (IMD) scores. Associations between IMD quintile, academic year and vaccination coverage were estimated using beta regression models.

Between 2020 and 2024, lower coverage was consistently associated with higher deprivation, and differences in coverage between the most and least deprived IMD quintiles more than doubled. In 2024 these differences were 17.7%, 18.2%, 16∙8% and 16.9% for HPV (females), HPV (males), MenACWY and Td/IPV, respectively. The consistency of these findings suggests the effect of deprivation on coverage is not vaccine-specific.

We demonstrated a consistent and strengthening association between coverage and deprivation across multiple adolescent school-based vaccination programmes in England over time. Contributory factors may be numerous, and further research is needed to understand which factors are driving trends for different populations. Addressing these inequalities will require sustained targeted interventions to improve awareness of and access to vaccination.

In South Korea, norovirus outbreaks have been predominantly attributed to the GII.4 genotype; however, since mid-2024, strains harbouring the GII.17 genotype are being detected more frequently, raising concerns about a potential shift in the dominant circulating strain and resulting public health implications.

We aimed to analyse the nt sequences of the gene encoding the viral protein 1 (VP1), the major capsid protein, of the GII.17 norovirus strains detected in South Korea in 2024, compare them with the corresponding nt sequences of the GII.17 Kawasaki 2014 lineage strains and evaluate whether GII.17 has the potential to replace the long-dominant GII.4 genotype.

We obtained 11 complete VP1 sequences from stool specimens collected across six regions in South Korea (Busan, Daejeon, Gangwon-do, Gyeongsangbuk-do, Incheon, Jeollanam-do) in 2024 and compared them with the VP1 sequence of the reference strain (GII.17 Kawasaki 2014) to identify genetic changes.

Key amino acid substitutions (R299P, N378D and K388R) were identified in the P2 domain of the VP1, which is a major antigenic site. Notably, N378D corresponds to D374 in the GII.4 genotype, which is a position involved in histo-blood group antigen (HBGA) binding, and K388R, adjacent to other antigenic sites, may alter the surface charge of the capsid.

The data provide molecular evidence that the emerging GII.17 strain in South Korea may evade the host immune surveillance machinery and exhibit altered receptor binding, underscoring the public health threat posed by this strain and the need for enhanced genomic surveillance and effective vaccine development.