Site screening has been standard procedure on job sites for the past year. Employers could soon be looking to proof of vaccine policies as well, but numerous question marks remain After a slow start, the vaccine rollout in Canada has started to hit its stride. The number of doses administered has regularly hit fresh daily records this month, and with more supply available, half of Canadians had received at least their first dose by May 22. Health authorities opening clinics to all ages mean millions more will follow heading into summer, along with second doses for those already with one jab.