Will public health measures (face masks, social distancing, avoiding gatherings) still be necessary after people start getting the vaccine?
Yes, for several reasons:
It is not yet known if the Pfizer and Moderna vaccines can prevent asymptomatic infection and subsequent transmission of the virus.
The vaccine is not 100% effective.
Public health measures will be important as long as virus is circulating in the community. There is currently widespread community transmission.
Vaccines are most effective in reducing virus when combined with public health measures until herd immunity is achieved.
No one knows you have been vaccinated when you appear in public, and the site of someone failing to wear a mask may cause anxiety for other individuals. Until there is widespread immunity to infection, masks and social distancing will be necessary. Optimal hand hygiene is always a good idea.