We don't know, but I think comparing the effectiveness of a regular flu vaccine, which requires guessing on strain a year in advance is not the same as targeting a specific current coronavirus. That said, this virus could mutate, like they all do, and move away from the vaccine's effective range. It seems Dr. Fauci is "cautiously optimistic". Good enough for me.Where do you get this number? The flu vaccine that people typically get each fall is only about 50%-60% effective, low enough that some people debate whether it should be called a "vaccine." I wouldn't expect a COVID-19 vaccine to be any better than that, but we won't know until one is developed.....
A study was done on the regular Flu vaccine, which varies in it's effectiveness from year to year (because of the strain guessing). It found that it had a meaningful reduction in Flu severity, even when didn't prevent the Flu. Specifically, if you caught the Flu anway, after being vaccinated, you have a 37% lower risk of being hospitalized and an 82% lower risk of being in the ICU (ventilator). If 82% fewer people go to the ICU, that means and even greater percent survive. Get that much done on Covid-19 and life moves on, even though many might still get temporarily sick.
Everything you need to know about the flu illness, including symptoms, treatment and prevention.
We only need to keep people from dying and over running the hospitals, we do not need to prevent everyone from getting sick. The later is impossible.