There may be confusion today about what CDC's new mask guidance means about the protection of vaccination. There are multiple levels of protection, and it’s important to know which level is up for discussion. Quick review. 1/6
1. Any infection. If you are vaccinated, would your body fight off the virus so that you would never even test positive or become infectious? This scenario is what original CDC guidance allowing vaxxed people to unmask was banking on being most common. 2/ cdc.gov/coronavirus/20…
2 Asymptomatic or presymptomatic infection and infectiousness. Say you get infected and would test positive but you have no symptoms. Could you transmit? We don’t rly know how common this is. Masks have particular value here because most people would not know they are infected 3/
3. Symptomatic and infectiousness. Say you are vaccinated, get infected, would test positive, and you have symptoms. You are likely infectious. Masks are important here as source control, but more importantly you must get tested and isolate at home. 4/
New topic, but relevant: Allowing vaxxed people to unmask may have had the side effect of everyone unmasking, vaxxed or not. Today’s mask guidance may also be intended to get more unvaccinated people to mask up again. 5/
Vaccines continue to be great at preventing severe illness, but delta may be making scenarios 2 and 3 somewhat more common. That possibility, the precautionary principle, getting unvaxxed to mask and rising hospitalizations all likely factor in to updated mask guidance. 6/6
In CDC's press conference just now, Dr. Walensky emphasizing scenario 3 as motivation for the new guidance.
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