News Ontario health officials say 21 day wait needed for vaccine to kick in SHARE ON: Mo Fahim, staff Monday, Jun. 7th, 2021 Photo credit; Ontario Legislature Ontario’s Chief Medical Officer Dr. David Williams says all the indicators show there is no reason not to reopen on Friday. Dr. Williams also said the reason behind the 21 day wait period between stages is to allow for the vaccinations to kick in and the case numbers to settle. Associate Medical Officer Dr. Barbara Yaffe added that it takes two, sometimes even three weeks for the vaccine to take hold and start working. “Yes it’s great that everybody is vaccinated today but we need to give their bodies time to develop the protection so that they are actually protected, that’s part of the reason for the 21 days,” Yaffe said. Williams says if we go from Step One to Step Two, we don’t want to go back to Step One, so the 21 days will give officials enough time to study trends.