[SpicyLemonZest]

I think you're misunderstanding the problem space here. We don't expect a coronavirus vaccine to prevent close to 100% of infections, so it's not a binary question of working vs. not working. The question is, how strong of an effect at what level of confidence is required to conclude that it's working well enough?

[JMTQp8lwXL]

The effect needs to be strong, because in ordinary times, many social circles cross paths and a much higher level of human contact occurs. The average person won't read into the nuance of 'the vaccine is X% effective, depending on risk factors Y and Z'. They'll rush to their ordinary behavior. While there isn't a vaccine, it's easier to obligate folks into social distancing. That strategy won't exist anymore once we have a vaccine, regardless of its efficacy.

[SpicyLemonZest]

I agree, but that's what the challenge is. We have to solve for the values of X, Y, and Z where we're comfortable with people's inevitable rush back to their ordinary behavior, and it's extraordinarily hard to figure out what those values should be.

[gniv]

> We don't expect a coronavirus vaccine to prevent close to 100% of infections

Why not? I would have thought we do. Most vaccines do (flu notwithstanding).

[SpicyLemonZest]

I don't know the biological reasons behind it (I don't even know if the reasons are known, or if it's just based on early results), but Dr. Fauci's said that scientists are hoping for 75% effectiveness and 50-60% effectiveness would be acceptable. (https://www.cnbc.com/2020/08/07/coronavirus-vaccine-dr-fauci...)