By Dr. Mallika Marshall

BOSTON (CBS) — Dr. Mallika Marshall is answering your coronavirus-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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“I am hearing more and more of people getting very ill after their second vaccine and I am also hearing that the Moderna and Pfizer are over 90% effective after the first shot. So why put people through that kind of illness if the percentages are so high.” – Marie

Early data suggests that a single dose of the Pfizer vaccine, for example, is very effective, but two doses is even better. Until we have more information, we still recommend betting both doses of either the Pfizer or Moderna vaccines. And while people do tend to develop more side effects after the second dose, they’re usually mild and last only a day or two.

Lynn says she’s scheduled for her first dose this week. She writes, “After I get my second dose, is it prudent to continue double masking with a medical mask when out in public, or will a single cloth mask will be sufficient?”

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I don’t think you should change your behavior after vaccination. I would say to anyone, vaccinated or not, that it’s a good idea to double-mask if you’re indoors or in a crowd or around others who are not wearing masks. If you’re outdoors or you can easily keep your distance from others who are also masked, a single well-fitting mask may be adequate.

“I will be getting my second shot five days before I leave for Aruba. I need to be tested 72 hours before I leave. Is there a chance I could be sick from the shot and not be able to go?” -Mike

It would be safer to travel, in general, after you are fully vaccinated against COVID-19. That said, getting a vaccine will not affect a COVID-19 test. The vaccine will not cause you to test positive for the virus. You may develop side effects from the vaccine as your immune system ramps up, but you can’t catch the virus from the vaccine.

Michael writes, “I will be getting the J&J vaccine and I am scheduled for a cortisone shot in my left knee that day.” He wants to know if that’s a problem. 

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It should not be a problem to get a cortisone shot in your knee on the same day as getting a COVID-19 vaccine. In general, if you’re feeling well and you have routine medical or dental appointments that same day, you should be fine. I would hesitate to schedule anything for the 1-2 days after your vaccine just in case you develop side effects and don’t feel great

Dr. Mallika Marshall