Ontario residents who got AstraZeneca vaccine can get Pfizer or Moderna booster at 12-week mark

Thestar.com
June 4, 2021
Rob Ferguson

Ontario residents who got a first dose of AstraZeneca’s COVID-19 vaccine and want to switch can get a booster shot of the Pfizer or Moderna vaccines at the 12-week mark.

The dosing interval was one of the last remaining questions after the National Advisory Committee on Immunization said earlier this week that different types of vaccines can be mixed in the wake of concerns about increased risk of rare blood clots from the AstraZeneca vaccine, mainly after first inoculations.

Ontario’s chief medical officer Dr. David Williams confirmed Thursday that the province will adopt the mixing recommendation starting Friday.

“It is vital that everyone who received the AstraZeneca vaccine for their first dose receives a second dose of a COVID-19 vaccine,” Williams said in a statement.

Recipients of the AstraZeneca or related Covishield vaccines can make appointments using the “second dose only” option on the provincial booking system starting next week or through local health units using their own systems.

They can also choose to get a second shot of the AstraZeneca vaccine at 12 weeks for peak protection against COVID-19. Those appointments can be booked at the pharmacy or primary care provider where they got the first injection, or by searching for another provider.

Thousands of AstraZeneca recipients have been frustrated that the pharmacies where they got their first shots are not carrying the vaccine anymore.

Williams said any AstraZeneca recipients unsure of which option to pick for a second dose should consult their doctor. AstraZeneca is made with viral vector technology, while Pfizer and Moderna are based on newer mRNA techniques.

“We know that mRNA has not been associated with any significant adverse events to this point,” said Dr. Dirk Huyer, Ontario’s chief coroner who is serving as head of provincial outbreak response and sits on the vaccination task force.

“What we don’t know is the clinical evidence of immune protection with AstraZeneca and mRNA together,” he added, saying studies on that are “not complete.”

AstraZeneca recipients who get a Pfizer or Moderna booster can expect “more side effects,” Huyer said.

The province is releasing a recent shipment of 254,500 doses of AstraZeneca to pharmacies across the province after providing an initial second-dose release of about 55,000 to pharmacies in Toronto, Windsor-Essex and the Kingston-area health units for shots to people who got vaccinated March 10-19 as part of a pilot project.

Also on mixing, people who got Pfizer or Moderna as their first shots could get the other for their booster if their initial vaccine is not available, Williams said.