"Scientists and public health experts have discussed for the past couple years whether to pull B/Yamagata from the flu vaccine or wait for a possible reemergence, said Kevin R. McCarthy, an assistant professor at the University of Pittsburgh's Center for Vaccine Research. But McCarthy agrees that continuing to vaccinate people against B/Yamagata does not benefit public health.

Additionally, there is a slight chance of B/Yamagata accidentally infecting the workers who manufacture the flu vaccine. The viruses, grown in eggs, are inactivated before being put into the shots: You cannot get influenza from the flu shot. But worker exposure to live B/Yamagata might occur before it's rendered harmless. "

  the flu vaccine may also end up using recombinant components in proaction for H5 avian emergence, if it really starts to spread.

 There are major problems when incubating avian influenza with classic poultry egg production methods. the yield is greater and lead time is reduced, when a well known sequence can be amplified in vitro.

A strain of influenza appears to have disappeared from the planet since COVID. As a result, U.S. flu vaccines have been redesigned.