I’m a virologist. Public should know covid exposure dose matters. We have to conserve masks for healthcare workers, but masks can help anyone, reducing amount of virus released (even by breathing) or taken in. Immune system is more effective if infection starts w/ low dose. (1/3)

Keeping the exposure dose to a minimum means that virus has to divide many more times before getting to high levels... but immune system starts responding and therefore can flatten the curve, keeping the peak viral load lower, so it does less damage (fewer symptoms). (2/3)

That won’t help everyone. For various reasons, whether genetics, immunosuppressive medications, or underlying conditions, even low exposure levels will climb to high, dangerous levels. But on the whole, keeping everyone’s exposure dose down (if exposed) could save lives. (3/3)

Please keep in mind though that healthcare workers and anyone working with vulnerable people should have priority as long as masks are in limited supply. They must be protected.