Global Experts Finalize Composition of 2025 Influenza Vaccine

In a significant development for public health, scientists from around the globe convened at The Francis Crick Institute last week to finalize the strains of the influenza virus that will be included in the vaccines for the northern hemisphere this coming autumn. This meeting marks the first time in over 70 years that such a gathering of influenza experts has been held in the United Kingdom.

The World Health Organization (WHO) announced the selected strains following a week of presentations and discussions among representatives from various WHO Collaborating Centres. These laboratories are responsible for monitoring circulating flu virus strains and their responses to existing vaccines and antiviral treatments, which is crucial given the flu virus's tendency to evolve rapidly.

The WHO Collaborating Centres meet biannually to share findings, recommend prevalent strains, and assess the global situation regarding influenza. In addition to discussing seasonal flu, the experts also reviewed zoonotic viruses, including avian influenza, to evaluate potential risks and determine which candidate vaccine viruses should be prepared for potential outbreaks.

During the meeting, participants presented data on current circulating strains and their distribution worldwide, as well as the effectiveness of existing antiviral medications and last year's vaccines against these strains. Based on this comprehensive analysis, the WHO proposed three influenza strains for the two types of vaccines that manufacturers will produce. The recommendation includes trivalent vaccines, which consist of two A-type flu viruses and one B-type flu virus.

Notably, the composition of this year's vaccines remains largely consistent with the previous year, with one A virus strain being updated to reflect genetic changes that have made the prior strain less effective against current circulating viruses. This adjustment is critical, as the new strain is anticipated to be more prevalent in the northern hemisphere this autumn.

Additionally, the experts reported on the potential for zoonotic transmission of influenza from livestock and avian sources, assessing whether existing candidate vaccine viruses could be utilized or if new candidates need to be developed. This proactive approach ensures readiness for any future outbreaks that may arise.

With the strains now finalized, vaccine manufacturers can begin the industrial development process without delay, ensuring that the new vaccines will be ready for distribution as early as October 2025. This timely preparation is essential for protecting public health during the upcoming flu season.