Possible Inadequacy of Existing Vaccines Against Bird Flu in Humans

Existing vaccines for H5N1 bird flu may be inadequate if the virus starts infecting humans, as they were derived from strains that circulated in 2004 and 2005. Developing new, better-tailored shots for the current strain would be complicated, as most flu vaccines are grown in chicken eggs. Vaccine researchers are developing mRNA vaccines that could be updated to target whatever mutated strain of H5N1 gains a hold in people someday. A universal flu vaccine could also provide cross-protection against whatever version of bird flu one day finds its way into humans.