By Dr. Mallika Marshall

BOSTON (CBS) – Dr. Mallika Marshall is answering your coronavirus and coronavirus vaccine-related medical questions. If you have a question for Dr. Mallika, email her or message her on Facebook or Twitter.

Dr. Mallika is offering her best advice, but as always, consult your personal doctor before making any decisions about your personal health.

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Paul writes, “If you are vaccinated and test positive for COVID, how do you know when you’re no longer contagious and when the virus is gone? You don’t get a re-test unless you pay for it on your own.”

If you test positive, the same protocols apply whether you’re vaccinated or not. You need to isolate for 10 days. If you’re fever-free and feeling better, you can then come out of isolation. You do not need to re-test.

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Joanne in Quincy says after her second COVID vaccine shot, she felt tired and her feet were freezing. She asks, “Is it likely that a booster will have the same effect? It won’t stop me from getting it though.”

I think it’s unclear whether you will have the same side effects from a booster shot as you did for your initial doses. For example, some people who experience “COVID arm” after their first dose of the Moderna vaccine had a milder case after the second dose or didn’t experience it at all. Talk to you doctor about your concerns.

John asks, “Do we still have to sanitize groceries after taking them home?”

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No, unless you feel more comfortable doing so. The coronavirus is spread predominantly in the air through respiratory droplets. That said, you still could get infected by touching a contaminated surface, which is why we still recommend frequent hand washing and sanitizer. So when you open your mail or put away your groceries, just wash your hands like you normally would.

Dr. Mallika Marshall