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Why are some COVID cases more serious than others? Dr. Mallika Marshall answers your questions

Why are some COVID cases more serious than others?
Why are some COVID cases more serious than others? 01:44

BOSTON - Dr. Mallika Marshall is answering your medical questions. If you have a question, email her or message her on Facebook or Twitter.

Rachel on the Cape writes, "I have a mild case of COVID even though I haven't had a booster in over a year. My friend has a serious case even though she's had every vaccine known to mankind. And why are these vaccines always touted as being 100% safe and effective?"

I'm glad you're having a mild case of COVID-19, probably in large part because you have been vaccinated and still have some residual immunity even though you haven't received a shot in over a year.  

Whether someone gets really sick from COVID depends on a number of factors such as vaccination status, age, whether someone has had COVID in the past, and a person's underlying health, etc. And if your friend is sick now, even if she received the new vaccine, there wouldn't be enough time to build immunity yet. 

That said, it's still unclear why some people get milder infections than others.  

No vaccine is 100% safe and effective. Every vaccine carries some risk of side effects but in the case of the COVID, RSV, and flu vaccines, the risk of serious complications is exceedingly rare.  

And while all three vaccines are not 100% effective at preventing infection, they all will significantly reduce your risk of getting seriously ill this winter.

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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