New research comparing four different flu vaccines found that the ability of the vaccines to activate cells of the immune system that help to protect against infection varied greatly depending on the vaccine type and age of the patient. Researchers say these findings have the potential to guide vaccine recommendations, especially for older adults.

The 2024–2025 flu season was considered highly severe, causing at least 47 million illnesses, 610,000 hospitalizations, and 27,000 deaths.

A new study, published in The Journal of Immunology, found that while all four seasonal influenza vaccines produced similar antibody levels, their ability to activate cellular immunity varied greatly depending on the vaccine type and age group.