To enter the U.S., air passengers need to take only one test — which can be a rapid antigen test — no more than 1 day before travelling. Last week, England scrapped its COVID-19 pre-arrival test requirement for fully vaccinated travellers and changed the rules so they only have to take a rapid test after they arrive.

Last month, the Public Health Agency of Canada told CBC News that it doesn't accept rapid antigen tests for travellers because they are less sensitive than molecular tests.