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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Dana asks, “Is it possible to get a rash 13 days after my first vaccination? I’m allergic to laundry products and my husband accidentally used one of these products. I started to break out which has happened before. Is it safe to get my 2nd vaccination?”

It’s probably safe to get your second dose. Significant allergic reactions to a vaccine usually occur within four hours. If your rash is the typical reaction you get when exposed to certain laundry products, the laundry products are probably to blame. But I would call your primary care doctor so you can describe in detail what type of rash you developed and double-check the timing of the reaction.

LSB writes, “I just received my first COVID shot five days ago and just found out today that I was exposed to a 5-year-old who just tested positive. I spent all weekend with this child. What do I need to do? Do I need to get tested or quarantine?”

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You are not fully vaccinated yet so you will need to quarantine for 14 days from the day of your last exposure to the child. You should also get tested in the next few days and if you develop symptoms.

Marion writes, “If you developed ‘COVID arm’ after the first dose of Moderna, are you at a higher risk to develop a similar or worse reaction after the second dose?”

This annoying but otherwise harmless reaction to the Moderna vaccine is no worse with the second dose. Researchers at MGH tracked people and found that 50% of patients who had the reaction with the first dose experienced no reaction with the second, 25% had a milder reaction and 25% had a similar reaction. And when they did get a reaction the second time around, it tended to fade faster.

Michelle writes, “Three weeks ago I got the J&J vaccine, not by choice. Although I know I’m lucky to have been vaccinated, I find myself extremely disappointed, and do not feel as “Covid safe” with the J&J. Can I get the Pfizer or Moderna vaccine in the future?”

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Please don’t feel disappointed. It’s really hard to compare the J&J vaccine with the Moderna or Pfizer vaccines because of when and how the different studies were conducted so you shouldn’t think of one as being inferior to the other. The J&J vaccine is very effective at preventing severe COVID-19 and in a large study, there were no hospitalizations or deaths among those who were vaccinated. J&J is now looking at whether a booster shot could provide even more protection. Stay tuned.

Dr. Mallika Marshall