I'm copying from an earlier thread post where I conveyed information from an extended family member who is an Infectious Disease specialist on just this issue...here it is...
"If I heard right, it's not enough that the vaccine could be 90% effective...it matters 'how many people actually get vaccinated'. The medical community would like to see something on the order of at least 60-70% of the population inoculated, however, right now that seems to be the percentage of Americans who DON'T want to get vaccinated. Additionally, there needs to be a well-functioning test/contact tracing system in place.
btw...for comparison, the Measles Vaccine is 99% effective and a sufficient percentage of the population gets inoculated, so even though it has a "Contagion Factor ('R-naught)" on the order of 18 (very high) we are all able to go about our normal lives. COVID-19 has R0 factor near 5.7, I believe, so if we work hard at mitigation and all get the vaccine, we'll get through this."
Hope this helps...in any event be sure to follow the advice of medical pros...mitigate, vaccinate and get all your family and friends to do the same.