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How many booster shots may be in your future?


Most health experts have urged that a third dose of the COVID-19 vaccine is key to pushing through to the otherside of the Omicron wave of the pandemic.

With many Canadians now boosted, or at least booked for their third shot, how long will the immunity last until they’ll need to roll up their sleeves again?

Dr. Bruce Mazer is an Associate Scientific Director with the COVID-19 Immunity Task Force, he says those at high-risk of severe illness will likely need to keep boosting going forward. For the rest of the population it is wait and see, but healthy individuals should have protection for the next “three to six months.”

“For individuals who are healthy and have a good immune system, it’s highly likely that the third dose will hold them for quite a while. But only time will tell.”

When antibody levels will begin dropping again and how many boosters will be needed in the future are questions immunology experts are still trying to answer.

“We’ll see if we get a variant that escapes this immunity. Then we need to go the boost route again for healthy individuals,” says Mazer.

In Ontario, top science advisers say two-dose protection has waned considerably since December, heightening the importance of booster shots.


science table data
Ontario COVID-19 Science Advisory Table vaccine protection data.

The science table advised that Omicron appears to replicate much more efficiently than previous variants. And if infected people have high virus loads, there’s a greater likelihood they’ll pass it on to others, especially the unvaccinated.

Omar Khan, Professor of Biomedical Engineering and Immunology at the University of Toronto says while two doses may not be strong enough to prevent Omicron, a booster shot of an mRNA vaccine — Pfizer or Moderna — revs the virus fighting antibodies back up.

“You’re immediately defended against an exposure of Omicron or a re-infection of Omicron,” says Khan.

And what about those who have recently recovered from a COVID-19 infection. Is a third shot even necessary?

“If we have higher antibody levels we can compensate for that slight loss of efficacy which can than give you good protection,” says Khan.

Mazer recommends those with natural immunity from a previous COVID-19 infection still get a booster. But he advises waiting eight to 12 weeks after getting sick before getting the third dose.

A second booster, or fourth dose, is already being rolled out to many high-risk groups in many North American jurisdictions. In Ontario, the Ford government announced fourth doses for residents of long-term care or other congregate care settings on Dec. 30. The province said the move was made on recommendations from Ontario’s immunization advisory committee.

The province has confirmed that students and teachers will return to in-person learning next Monday, and though steps have been taken to get teachers a third dose, children remain ineligible for a booster shot.

Ontario adults who are 84 days removed from a second dose can currently get a COVID-19 booster shot. Last week, the province signalled an acceleration in booster shots for education and child care workers by setting up an additional 10 vaccine clinics in the Greater Toronto and Hamilton areas.



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