WASHINGTON—The United States will remain on the sidelines for now as Canada gamely welcomes back fully vaccinated American citizens and permanent residents. As of midnight Sunday night, non−essential U.S. travellers who have had a full course of a Health Canada−approved COVID−19 vaccine will again be allowed on Canadian soil. To be eligible, travellers must live in the U.S., have allowed at least 14 days to pass since their last dose and show proof of a negative molecular test for COVID−19 that’s no more than 72 hours old. They are also required to use the ArriveCAN app or online web portal to upload their vaccination details. Denis Vinette, vice−president of the travellers branch of the Canada Border Services Agency, says the agency learned a lot when fully vaccinated Canadian citizens were allowed to return last month. Vinette says about half had to be turned away during the first week because they …