April 30, 2026

Influenza

Pediatric Vaccine Effectiveness Against Influenza Hospitalization And Outpatient Visits: 2021–2024
Authors used data from seven U.S. pediatric medical centers within the New Vaccine Surveillance Network, including children aged 6 months to 17 years who were hospitalized or received outpatient care for acute respiratory illness (ARI). They estimated VE against influenza-associated hospitalizations and outpatient visits with subgroup analyses for each season, stratifying by health care setting, age, and influenza virus type/subtype/genetic clade. Among 19,917 children with ARI, 2,831 (14%) were positive and 17,086 (86%) were negative for influenza; 8,523 (43%) were vaccinated, and 11,394 (57%) were unvaccinated. Vaccination uptake among children testing negative for influenza ranged from 44% to 51% by season. VE overall ranged from 34% to 60% across seasons, with the lowest VE estimates during 2021 to 2022. Effectiveness was 53% against influenza A/H1N1, 43% against A/H3N2, and 69% against B, with further variation by clade. Overall, vaccine effectiveness was 57% against outpatient visits and 50% against hospitalizations among children and adolescents during the study period.

Influenza Vaccine Effectiveness in European Primary Care Pediatric Practices: 2022–2024
In this study, in 2022/23, overall VE against any influenza was 68%. In 2023/24, overall VE against any influenza was 71%.

RSV

Impact of Universal Nirsevimab Prophylaxis in Infants on Hospital and Primary Care Outcomes Across Two Respiratory Syncytial Virus Seasons in Galicia, Spain (NIRSE-GAL): A Population-based Prospective Observational Study
Authors included all infants eligible for nirsevimab in the 2023–24 RSV campaign in Galicia, followed up from their first RSV season (2023–24) until the end of their second RSV season (2024–25). The primary endpoint was RSV-related lower respiratory tract infection (LRTI) hospitalisation. Secondary endpoints were LRTI hospitalisation, acute bronchitis or bronchiolitis hospitalisation, pneumonia admissions, all-cause hospitalisations, and primary health-care outcomes (acute bronchitis or bronchiolitis, wheezing or asthma, LRTI, respiratory infections, acute otitis media, and all otitis diagnoses). Of 12,492 eligible infants, 11,796 received nirsevimab (94·4% coverage). Compared with historical cohorts, RSV-related LRTI hospitalisations decreased by 85·9% (95% CI 80·2–90·0) in the first season and 55·3% (22·5–74·3) in the second. They saw a reduction in several other endpoints as well.

First Report on Remdesivir Use for the Treatment of Respiratory Syncytial Virus in Five Allogeneic Hematopoietic Cell Transplant Recipients
Respiratory syncytial virus (RSV) infection causes substantial morbidity among hematopoietic cell transplant (HCT) patients and lacks approved therapies. Remdesivir demonstrates antiviral activity in vitro, but data in humans are lacking. Authors describe five HCT recipients with RSV lower respiratory tract infection who were treated with remdesivir with clinical improvement.

COVID: Early Viral Phase

Oral Nirmatrelvir–Ritonavir for Covid-19 in Higher-Risk Outpatients
Data are presented from two open-label platform trials (PANORAMIC in the United Kingdom and CanTreatCOVID in Canada). These trials enrolled higher-risk adults (≥50 years of age or ≥18 years of age with coexisting conditions) in the community who tested positive for SARS-CoV-2 and had been unwell for five days or less. The participants were randomly assigned to receive usual care plus nirmatrelvir (300 mg)–ritonavir (100 mg) twice a day for five days or to receive usual care alone. The primary outcome was hospitalization or death from any cause within 28 days after randomization. Conclusions: In two open-label trials, nirmatrelvir–ritonavir did not reduce the incidence of hospitalization or death among vaccinated higher-risk participants with SARS-CoV-2 infection. (Funded by the National Institute for Health and Care Research, and others; PANORAMIC ISRCTN number, 2021-005748-31; CanTreatCOVID ClinicalTrials.gov number, NCT05614349.)