Will the eventual covid-19 vaccine need to be taken annually, or once every several years?

Unknown: No one knows yet. It is too early to tell whether a vaccine, once developed, will be a one-time vaccine, or need a booster after a certain number of years, or if it will be annually (like the flu vaccine). As more research is done, that , and experience once the vaccine is widely available, will let us know.

Too early to know: Vaccines will need to be developed, tested and evaluated over-time to answer that question.