DEAR DR. ROACH: My daughter was recently visiting and tested positive for COVID. Since my last COVID vaccine was eight months ago, I searched for how much protection I still had and understood the response to be little to none. So, why is the recommendation for vaccination only once per year and not more frequent so that we always have some protection?

— B.J.M.

ANSWER: The mRNA COVID vaccines provide 85% to 90% protection for the first three months or so, but the immunity wanes to only 50% to 60% effectiveness against getting the disease after six to eight months. The vaccine efficacy depends on the particular vaccine and precise variant of COVID. So, you are right that the vaccine you got eight months ago provides little protection against getting the disease now.

However, the vaccine

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