Background: The 2025 influenza season is characterized by antigenic stability in major seasonal strains and the emergence of novel avian influenza variants. This review synthesizes current evidence on the epidemiology, virology, vaccine effectiveness, and public health challenges for both seasonal and avian influenza in 2025.
Materials and Methods: A narrative review was conducted using literature from PubMed, Scopus, Web of Science, WHO, CDC, and Google Scholar up to March 2025. Included studies were original research, systematic reviews, surveillance reports, and official guidelines on circulating strains, vaccine effectiveness, emerging variants, and interventions. Two reviewers independently screened and selected studies, extracting data on virus subtypes, vaccine composition, surveillance updates, and public health measures.
Results: A/H1N1pdm09 and B-Victoria lineages remained antigenically stable, supporting continued vaccine effectiveness, while A/H3N2 continued to drift, necessitating annual vaccine updates. The B/Yamagata lineage was undetected, prompting a transition to trivalent vaccines for 2025–2026. Emerging avian influenza variants, notably H10N3 and H5N1, highlighted ongoing zoonotic risks, but sustained human-to-human transmission was not observed. For the 2024–2025 season, vaccine effectiveness ranged from 36–54% in adults and reduced pediatric hospitalizations by 63–78%. Enhanced surveillance, including real-time genetic tracking and multidisciplinary analyses, improved outbreak detection, but challenges persisted in vaccine strain selection, production timelines, and equitable distribution.
Conclusion: The 2025 influenza season demonstrates the challenge of maintaining vaccine effectiveness amid stable strains and emerging avian variants. Vigilant surveillance, adaptive vaccine strategies, and coordinated public health responses remain essential. The shift to trivalent vaccines and adoption of advanced surveillance tools emphasize the ongoing need for innovation and equity in influenza control.