November 11, 2025

Influenza

Effectiveness of High-dose Influenza Vaccine Against Hospitalisations in Older Adults (FLUNITY-HD): An Individual-level Pooled Analysis
Two large-scale trials comparing high-dose inactivated influenza vaccine (HD-IIV) versus standard-dose inactivated influenza vaccine (SD-IIV) against hospitalisation outcomes were conducted in Denmark and Spain. Here they analyse the pooled data from these trials to enhance generalisability and assess the relative vaccine effectiveness (rVE) of HD-IIV versus SD-IIV against severe clinical outcomes in older adults. In this prespecified pooled analysis, HD-IIV demonstrated superior protection compared with SD-IIV against hospitalisation for influenza or pneumonia and also reduced the incidence of the secondary endpoints of cardiorespiratory hospitalisation, laboratory-confirmed influenza hospitalisation, and all-cause hospitalisation. Given wide eligibility for influenza vaccination, implementing HD-IIV could result in substantial public health benefits.

Relative Effectiveness of the High-dose versus Standard-dose Influenza Vaccines for the Prevention of Laboratory-confirmed Influenza Among Italian Older Adults During Three Recent Seasons
These are results of a test-negative designed study. Here the outcome is getting the flu. Among 1,238 vaccinated older adults included in the analysis, influenza positivity prevalence was lower (P = 0.022) in HD-IIV (6.6%; 46/693) than SD-IIV (10.3%; 56/545) recipients. rVE of HD-IIV versus SD-IIV was 29% (95% CI: −22%, 59%) among subjects aged ≥60 years. Among adults aged ≥80 years, for whom HD-IIV was preferentially recommended, HD-IIV was more effective than SD-IIV by 54% (95% CI: 10%, 76%).

RSV

Long-term Impact of Nirsevimab on Prevention of Respiratory Syncytial Virus Infection Using a Real-word Global Database
These are results of a multi-centre retrospective study using a global database (TriNetX). The participants were children under 24 months of age who required microbiological testing for RSV (PCR or antigen testing) between July 2023 and June 2025. Children who received the last dose of nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months were compared with those who did not receive any nirsevimab dose by epidemic season after propensity score matching. This study indicated that the preventive effect of nirsevimab against RSV infection was maintained for up to 12 months following administration, whereas a preventive effect beyond 12 months was not observed. The results of this study need to be interpreted with caution owing to some important limitations.

COVID: Active Vaccination/Immunity

COVID-19 and Influenza Deaths in Australian Children 2018-2023: A National Case Analysis
Here the authors aimed to estimate and compare mortality rates attributable to COVID-19 and influenza in the Australian pediatric population. A case series of children aged <18 years hospitalized with laboratory-confirmed SARS-CoV-2 or influenza and recorded as deceased. COVID-19 cases were ascertained January 2020 – September 2023 and influenza, seasonally, from 2018 – September 2023 at eight sentinel children’s hospitals in Australia. In children who died with SARS-CoV-2 or influenza infection, attributable in-hospital mortality proportions were 11/19 (58%) and 23/29 (79%) respectively. Among COVID-19 and influenza attributable deaths, 47% (16/34) had no known pre-existing co-morbidity. Of the 10 deaths where COVID-19 vaccination status was known, four (40%) were vaccinated. Most of the deaths were due to Omicron. For flu deaths the vaccination rate was only 19% in those that died. The Australian estimate of the attributable mortality rate for COVID-19 in children is similar to that reported from the UK of 2–5 deaths per million while in the U.S. the estimate is 10 deaths per million children.