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As US leaders work to control the spread of coronavirus, researchers across the country - and globe - are working to answer the mysteries that remain around infections.

One of those mysteries: why the experience can be so different from person to person. One expert says the answer may involve looking at previous vaccines individuals have had. Once you're infected, how much of the virus made it into your body could also have an impact on what your experience is, another expert told CNN on Monday, and masks could make a difference.