There is however some promising work on designing antibodies which might be broadly effective against all flus including H5N1: https://pubmed.ncbi.nlm.nih.gov/2

There is however some promising work on designing antibodies which might be broadly effective against all flus including H5N1: https://pubmed.ncbi.nlm.nih.gov/21320540/ https://pubmed.ncbi.nlm.nih.gov/21320540/ But that's a decade away from deployment - though fortunately likely highly motivated if it works because the other promise is long-term immunity, rather then yearly boosters.