Health officials in Canada are suspending the rollout of AstraZeneca Plc’s COVID-19 vaccine to younger people over concerns it could lead to blood clots in rare circumstances.

AstraZeneca shots have been halted in most of the country, including the provinces of Ontario, Quebec and British Columbia, after the nation’s vaccine advisory committee recommended that public health authorities stop giving it people under 55 years old.

It’s another setback for Prime Minister Justin Trudeau’s vaccine effort, which is off to the second-slowest start among Group of Seven nations. And it comes as a new wave of the virus is accelerating in the country. Canada reported an average of 4,352 new cases a day over the seven days ended March 28, up 23 per cent from the previous week.

Just 1.8 per cent of Canadian residents are fully vaccinated, compared with 15.8 per cent in the U.S., according to Bloomberg’s Vaccine Tracker. Most of the vaccines distributed in Canada so far have been the Pfizer Inc. or Moderna Inc. shots, which were approved by health authorities months before the AstraZeneca shot.

British Columbia, which has kept restaurants open for most of the pandemic, said Monday it would close indoor dining, worship services and most indoor fitness activities as of midnight local time. Vail Resorts Inc.’s Whistler Blackcomb ski resort will be shut.

“We need a circuit breaker to stop this virus now,” Bonnie Henry, B.C.’s provincial health officer, said at a news conference. The region recorded more than 2,500 new cases over the weekend and new variants are on the rise.

‘Rare but Serious’

News of the change in the vaccine panel’s recommendation on AstraZeneca was first reported by the Canadian Broadcasting Corp. Provincial decisions to halt shots came before the formal announcement.

Joss Reimer, head of Manitoba’s vaccine task force, said a “rare but very serious side effect” was seen mainly among young women in Europe. “Out of an abundance of caution, Manitoba will be recommending that these vaccines only be used in people who are 55 and older at this time,” she told reporters Monday in Winnipeg. “This is a pause while we wait for more information.”

The move could cast further doubt about the safety of the vaccine after concerns were raised in Europe about potential side effects. Only two weeks ago Trudeau sought to reassure Canadians the AstraZeneca vaccine was safe for use.

Canada is due to receive 1.5 million doses of the vaccine from the U.S. this week. The federal government is responsible for procuring and approving vaccines, while provinces are in charge of administering the shots and setting the rules for vaccine rollout.

“I’ll tell you, I won’t hesitate to cancel that in half a heartbeat if it’s going to put anyone in harm,” Ontario Premier Doug Ford said at a news conference in Niagara Falls.

Last week, Denmark extended its suspension of the AstraZeneca vaccine for another three weeks and Sweden has decided to use it only on people older than 65.