Also if you check up on these studies they all have serious flaws (my question was a leading one). The protective effect is essentially unknown empirically but mechanically it's sound. Anything decreasing exposure should help, since that seems to be a defining factor in whether someone gets infected and is why indoor spaces are so much riskier.
Says who based on what?
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Right, 30% protection isn't bad.
Also if you check up on these studies they all have serious flaws (my question was a leading one). The protective effect is essentially unknown empirically but mechanically it's sound. Anything decreasing exposure should help, since that seems to be a defining factor in whether someone gets infected and is why indoor spaces are so much riskier.