There is an evidence that or immune system has either limited memory or bandwidth or both. See immune imprinting. So while taking once a ten year vaccine for no

There is an evidence that or immune system has either limited memory or bandwidth or both. See immune imprinting. So while taking once a ten year vaccine for not rapidly mutating pathogen makes it more robust, the case of regular intake for highly volatile virus is not so obvious. There were already warning cases with flu and some other diseases.