The World Health Organization (WHO) has recommended removing a component from flu vaccines due to the apparent extinction of certain flu viruses during the Covid-19 pandemic. Specifically, the influenza B/Yamagata viruses have not been seen since March 2020 when global flu circulation declined significantly in response to the Covid-19 outbreak and the preventive measures people took to avoid contracting the virus.
The recommendation was made during a week-long meeting of flu experts from around the world, who convene biannually at the WHO to examine circulating flu viruses and advise on future flu shot formulations. The experts concluded that there is currently no benefit to including the B/Yamagata viruses in the vaccine, and there is even a theoretical risk associated with doing so. Manufacturers must cultivate B/Yamagata viruses for vaccine production, which could potentially lead to leaks from manufacturing plants or the reintroduction of the virus through intranasal flu vaccines.
Florian Krammer, an influenza virologist at Mount Sinai School of Medicine in Manhattan, applauded the WHO’s decision, stating that including a virus that no longer exists is unnecessary. The committee urged regulatory bodies to work with vaccine manufacturers to remove the B/Yamagata component from flu vaccines as soon as possible.
Furthermore, the recommendation will not affect many low- and middle-income countries, as they still use trivalent vaccines that protect against select flu viruses. However, countries that have transitioned to quadrivalent vaccines may need to adjust their manufacturing processes, pending regulatory approval.
The FDA is currently discussing the possibility of removing the B/Yamagata component from flu vaccines. However, the process may be complicated, as it depends on whether vaccine manufacturers still hold licenses for trivalent formulations. While changing the composition of the vaccine will take time, experts emphasized that there is no disadvantage to receiving a quadrivalent vaccine and that individuals will still be protected.
In recent years, there have been discussions within the scientific community about replacing the B/Yamagata component with other flu viruses, such as a second H3N2 vaccine or potentially pandemic threats from bird or swine flu viruses. However, these ideas are still in the research stage and not yet ready for consideration by the vaccine composition committee.
Overall, the removal of the B/Yamagata component from flu vaccines is a response to the global decline in flu transmission during the Covid-19 pandemic. By making this adjustment, vaccine manufacturers can align the formulation with the circulating flu viruses to ensure optimal protection for the public.