Does The Flu Shot Affect The COVID Vaccine's Effectiveness? Dr. Mallika Marshall Answers Your Questions

BOSTON (CBS) — Dr. Mallika Marshall is answering your coronavirus vaccine-related medical questions. If you have a question, 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.

Darlene writes, "My adult daughter had mild COVID then had emergency back surgery. She had to get the vaccine to keep her job, against her surgeon's recommendation. How will it interfere with her fertility and how sick is she likely to get from the shot with compromised immunity?

Don't worry. The vaccine will not affect her reproductive system or her ability to have children. And if she has a compromised immune system, she is actually less likely to develop side effects from the vaccine. Side effects develop as the body mounts an immune response to the vaccine. And she is much more likely to get sick if she got reinfected with the coronavirus. People who have had COVID are still advised to get vaccinated within 90 days of their infection. She should be fine.

Charyl says, "I got the booster and several days later developed a hoarse voice. My husband's boss had COVID a week ago. My husband tested negative, but should I be tested for COVID or could my laryngitis be from the vaccine?"

I think if you think you may have been exposed to COVID, through your husband or otherwise, you should get tested. You can buy a rapid antigen test at the drugstore and test yourself at home, or you can go get a PCR test. It is certainly possible that your symptoms are related to the booster, in which case they should go away soon, but if you're concerned, get tested so you can have some peace of mind.

Dave in Milford writes, "I received my flu shot in September and my Pfizer COVID booster two days ago. How long until I gain full effectiveness of the Pfizer vaccine and will the flu shot interfere with that?"

It generally takes about 2-3 weeks to build full immunity after vaccination, to both the COVID-19 vaccine and the flu vaccine. And no, the flu vaccine should not interfere with your ability to mount a robust immune response to the COVID-19 vaccine. As you know, young children often receive several vaccines at the same doctor's appointment without concern that one is going to interfere with the other. Your immune system can multitask.

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