Covid-19 (and other covirus) are dangerous, like the flu. So there is a recommendation for an anual flu vaccine for old people and other special cases. It make sense to have a similar recommendation for a few species of coronavirus that are around.

A study shown that getting the flu vax makes you 27% more susceptible to get the flu.

Do you have a link to the study. I'd like to take a look and report anything interesting.

First question: Double blind randomized controlled group?