August 20, 2026

Influenza

Oseltamivir for Critically Ill Patients with Influenza: A Randomised Trial
The antiviral oseltamivir (Tamiflu) is widely used for the treatment of critically ill patients with influenza. Evidence from randomized trials about its efficacy in the critically ill is lacking. In an ongoing international, multifactorial, Bayesian adaptive platform randomised trial, authors evaluated oseltamivir for five days, oseltamivir for 10 days, or no antiviral treatment in critically ill patients aged 12 years and older with confirmed influenza severe respiratory infection. Between March 1, 2020 and March 13, 2026, 442 participants were randomized to receive five days of oseltamivir (n=162), 10 days of oseltamivir (n=156), or no antiviral (n=124). By day 90, 17 (13·7%) in the no antiviral group, 32 (19·8%) in the five-day oseltamivir group, and 30 (19·4%) in the 10-day oseltamivir group had died. The median adjusted OR for 90-day mortality was 2·13 (95% CrI 1·03 to 4·52) for five days of oseltamivir and 2·17 (95% CrI 1·05 to 4·64) for 10 days of oseltamivir, favoring no antiviral. For the five- and 10-day oseltamivir treatments, the posterior probabilities for harm, an adjusted OR >1, were 98·0% and 98·2%, respectively. Interpretation: Treatment with oseltamivir is ineffective and highly likely to increase 90-day mortality in critically ill patients with influenza.

RSV

First- and Second-Year Outcomes After Nirsevimab Immunization
This cohort study analyzed two nationwide matched cohorts using the French National Health Data System. Infants receiving nirsevimab were matched 1:1 to unimmunized infants. Both cohorts were followed up for one year after immunization, with an additional second year of follow-up for the 2023 cohort. This cohort study included 74,672 infants in 2023 and 175,526 in 2024. At baseline, the mean (SD) age of immunized infants was 4.5 (2.0) months in the 2023 cohort; 19,633 (52.6%) were male and 17,703 (47.4%) were female. Nirsevimab was associated with a lower rate of RSV-LRTI–related hospitalization in both the 2023 and 2024 cohort during the first year of follow-up, with effectiveness estimates of 66% (95% CI, 61%-70%) and 72% (95% CI, 69%-75%), respectively. An association with higher rates of hospitalization for ear, nose, and throat (ENT) bacterial infections was observed (2023 cohort: weighted hazard ratio [wHR], 1.36; 95% CI, 1.00-1.84; 2024 cohort: wHR, 1.43; 95% CI, 1.15-1.78). No significant association was observed for other outcomes. During the second year of follow-up, no protective association was observed for RSV-LRTI–related hospitalization (wHR, 1.03; 95% CI, 0.73-1.43).

A National Programme of Bivalent Prefusion F Vaccination in Pregnancy and Protection Against Respiratory Syncytial Virus Hospitalisation in Infants Until Age 6 Months in the UK: A Multicentre, Prospective, Test-negative, Case–control Study
In 2024, the UK introduced the maternal bivalent respiratory syncytial virus (RSV) prefusion F (RSVpreF) vaccine for all pregnant individuals at a gestation of 28 weeks or more. Researchers conducted a national, multicenter, prospective, test-negative, case–control study at 37 BronchStop hospital sites in the UK. Between Sept 2, 2025, and Jan 31, 2026, 1,356 infants were admitted to participating sites and screened for eligibility, 694 of whom were included in the primary analysis (429 RSV-positive infants and 265 RSV-negative infants). Median age was 2·2 months (IQR 1·3–3·9) for RSV-positive infants and 1·7 months (1·0–3·3) for RSV-negative infants. 394 (57%) of 694 infants were male and 300 (43%) were female. The mothers of 161 (38%) RSV-positive infants and 175 (66%) RSV-negative infants had received the RSVpreF vaccine before delivery. The adjusted vaccine effectiveness of maternal RSVpreF vaccination for preventing infant hospital admission was 61% (95% CI 38–75) for infants aged up to 6 months, and 76% (54–87) for infants aged up to 3 months. The overall effectiveness of the UK RSV prevention programme was 61% (39–75) through to age 6 months.