Second doses of COVID vaccines prioritized for long-term care, says Dr. Henry as delays continue

VANCOUVER (NEWS 1130) – As supply and operational issues continue to stymie COVID-19 vaccine delivery, B.C.’s top doctor says there is growing evidence it’s safe to delay the second shot for up to three months.

As Canada continues to trail dozens of countries in the world in vaccination rates per 100 people, Provincial Health Officer Dr. Bonnie Henry has adapted B.C.’s rollout plan to limit to whom second doses will being given over the next several weeks.

As the situation continues, she says booster shots will be prioritized those in long-term care homes while others who have already had their first dose may have to wait for weeks or months outside the manufacturer’s recommended dosing window.

“It may, in fact — and we know this from other vaccine programs and from how our immune system works — result in the end in a stronger and more long-lasting protection,” Henry said Tuesday.

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She explains the first dose triggers the production of antibodies that result in increased immunity but the second dose triggers the adaptation of the body’s cellular defences through T-cells and B-cells in our blood.

“These are cells that live in our lymph node and in our blood system and they take time to fully develop and they also modify and they react to things like the protein on the outside of the virus and it’s these cells that take longer to build up but are longer lasting as well,” she explained.

She says as a scientist she’s still impressed by the 89-90 per cent effectiveness that has been recorded in first-dose recipients in B.C. and other places.

For people worried about losing immunity between doses, Henry says there’s growing evidence from the U.K., Israel, Quebec, and here in B.C. that shows protections could last up to three months after just one dose.

“We can safely delay the second dose, if needed, to make sure that our operational issues, that enough vaccine comes to be able to provide those second doses. And in the U.K. and in Quebec, they’re looking at 90 days, or three months, for the second dose,” she said, noting the initial target was to get the second dose of vaccines into British Columbians within 35 days.

Henry says most people who have taken their first Pfizer shot will get their second before 42 days.

“We have some challenges with Moderna because the amount of Moderna, it was coming in every three weeks, and the amount we’re getting next week is lower than expected,” she said, adding there will be a delay causing somewhere between four- and six-thousand people receiving both doses to have to wait.

Henry says the exact numbers will depend on just how many doses of the Moderna drug come in March.

“The one thing I am confident of is the increasing data that supports that we have a very strong and robust immune response to the first dose that lasts for the short term. And when we’re talking short term, it is definitely in the longer than six weeks and at least out to three months. So I’m not concerned that we’re going to decrease our vaccine effectiveness,” she added.

Health Canada’s page on COVID-19 vaccine recommendations, last updated Jan. 12, maintains that protection offered by the first dose is lower than what’s achieved when both shots are given. The federal agency notes there is “very limited data on duration of protection from one dose.”

It does say that the first dose of approved COVID-19 vaccines in Canada — currently the Pfizer-BioNTech and Moderna drugs — “has been shown to offer at least short-term protection,” as Henry has explained.

Meanwhile, Henry stressed the importance of further looking at just how long protections last after the initial dose of the two-dose vaccines.

As of Tuesday, B.C. had administered 171,755 doses COVID-19 vaccines. Of those, 22,914 are second shots.

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