Canada approves Pfizer vaccine

The United States’ northern neighbors should start getting immunized against the coronavirus within days, and the United Kingdom began rolling out the shots this week. The U.S. Food and Drug Administration’s independent advisers plan to meet Thursday to debate whether Pfizer and its partner BioNTech have presented sufficient evidence of the vaccine’s safety and effectiveness to grant emergency use authorization. If they approve it as expected, distribution could begin within days.

Is the vaccine effective? A few days ago, FDA officials affirmed Pfizer’s claim that its vaccine is very effective at defending against COVID-19 and has no known, serious side effects. However, Britain’s medical regulator warned on Wednesday that people with a history of severe allergic reactions shouldn’t get the shot. Two people who received the vaccine during the United Kingdom’s first day of distribution had adverse reactions, though they have recovered, said Stephen Powis, medical director for England’s National Health Service. Both carried adrenaline shots for severe allergies.

Dig deeper: Read Charles Horton’s explanation of how regulators judge the safety and effectiveness of vaccines.