In a significant development, advisers to the FDA have recommended the removal of a specific type of flu virus, known as the “Yamagata lineage,” from future flu vaccine formulations in the United States. This decision follows the apparent extinction of Yamagata viruses, which haven’t been detected anywhere on Earth since March 2020.
The Yamagata lineage, a branch of the influenza B family tree, has been a target of concern since its disappearance was first noted by scientists in 2021. Speculation arose that public health measures implemented during the COVID-19 pandemic, such as masking and social distancing, might have contributed to the eradication of this particular flu strain.
Now, a panel of advisers to the FDA has unanimously endorsed the exclusion of Yamagata viruses from flu vaccines for the 2024-2025 flu season. This adjustment reduces the number of flu strains targeted by US vaccines from four to three, aligning with a recommendation made by the World Health Organization in fall 2023.
Dropping the Yamagata lineage from vaccine formulations offers several benefits. It could enhance manufacturing capacity, enabling the production of more vaccine doses. Additionally, it eliminates potential risks associated with cultivating the virus in labs, a process currently necessary for vaccine production.
Experts emphasize that vaccinating against an extinct virus is unnecessary, underscoring the rationale behind this decision. The move has been under discussion for years, with health officials advocating for the change.
Despite concerns raised by pharmaceutical industry leaders about the transition to a trivalent formulation, FDA advisers are pushing ahead. Manufacturers are gearing up to produce trivalent vaccines for the upcoming flu season in the US, with plans for other countries to follow suit in accordance with their regulatory processes.
Confirmation from Jerry Weir, director of the FDA’s Division of Viral Products, indicates that all US flu shot manufacturers have taken necessary steps to produce trivalent vaccines. As these adjustments unfold, global surveillance efforts will continue to monitor flu viruses, including the now-extinct Yamagata lineage, to ensure public health preparedness.
