National committee recommends longer interval between COVID-19 vaccine doses

P.E.I.'s plan to have every adult receive their first vaccine dose by the beginning of July was supported by recommendations from the National Advisory Committee on Immunization (NACI) late Wednesday.

NACI announced that it was changing its recommended interval between doses, increasing it to four months in order to get first doses into as many people as possible.

In a statement, NACI said "in the context of limited COVID-19 vaccine supply, jurisdictions should maximize the number of individuals benefiting from the first dose of vaccine."

Dr. Shelley Deeks, the vice-chair with NACI, said the committee has been working on updating the recommendation for about a week and finalized the decision Tuesday, the same day P.E.I. announced its change in vaccination plans.

"I updated the chief medical officers of health on Sunday that this is the direction that NACI was going," Deeks said.

"I'm very confident that P.E.I. made the decision based on the knowledge that this was coming and that it was in the best interest of the people of P.E.I."

NACI said it is continuing to assess the evidence and adjust vaccine recommendations as needed.

'Emerging evidence'

P.E.I. is currently using the Pfizer-BioNTech and Moderna vaccines — both of which require two doses and were previously recommended at 21 and 28 days apart respectively. 

Chief Public Health Officer Dr. Heather Morrison addressed the concern of Islanders about the change during a public health briefing on Wednesday.

She said people who had an appointment scheduled for their second dose will receive the vaccine as planned.

For all subsequent vaccinations, there will be an extension of the interval between the first and second dose.

"There is emerging evidence out of this country and elsewhere that shows that there is not only good effectiveness a couple of weeks after you get your first dose but that persists," Morrison said.

The decision to extend the time between the doses, she said, is based on the latest available science.

"We know we want to protect Islanders — as many of us, as fast as we can," Morrison said. "We would only be making that recommendation if we thought it was good for everybody."

On Wednesday, Manitoba and Newfoundland and Labrador also announced they were extending the interval, while British Columbia made the announcement earlier this week.

Help population overall

Dr. Sumon Chakrabarti, infectious diseases physician in Mississauga, Ont., said extending the time between doses is a way for more people to be protected at a population level.

"Say you have a population of 100 people and all of them are partially protected as opposed to half being full protected and half unprotected," Chakrabarti said. "You are going to really affect the pandemic in a much better way."

There is precedent from other vaccines, he said, and more evidence accumulating around the use of the COVID-19 vaccines.

"The second dose tends to be the one that boosts the first dose — makes it more robust and long term," Chakrabarti said.

"Now what we need to do, we are in a public health emergency, we want to try to get as many people protection as we can."

Chakrabarti said all three of the approved vaccines in Canada are extremely effective in preventing death and hospitalization.

Research pivoting

Dr. Rod Russell, a professor of immunology and infectious diseases with Memorial University in Newfoundland, said the original recommendations for the interval time came from limited clinical trials.

"The real world data now is actually outweighing the clinical trial data because most of clinical trials were 40,000 people in Phase 3," Russell said.

"Whereas now you've got millions of people that have been vaccinated and we're seeing 80 per cent protection after one dose in some places."

He said the research on coronavirus has been pivoting and shifting — sometimes on a weekly basis — as the virus changes in front of them.

Right now, he and his colleagues are looking at how the vaccine works against all the different variants. 

"How fast will we be able to get back to normal is the real question," Russel said. 

"I think we have to get as many people vaccinated as possible so I support the idea of delaying the second dose." 

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