At least Gaten, Noah and Millie were vaccinated over the weekend (don't know about the others). Getting the cast and crew vaccinated SHOULD allow them to speed up production of season 4.
I’m so happy for them and I hope they will get fully vaccinated for season four when they get their second dose. So the production can speed up and can have “ Fully vaccinated pass”. But probably still get Covid-19 testing but I don’t know.