A joint letter from senior scientists from a number of major health institutions is raising questions about a plan to delay second doses of COVID-19 vaccinations by four months.
A draft of the letter obtained by Global News from an Ontario government source highlighted the unknowns surrounding the plan and the thoroughness of it.
The document was signed by doctors with the University of Toronto, University Health Network (UHN), Sunnybrook Research Institute, Princess Margaret Cancer Centre and Montreal Clinical Research Institute.
The letter came just days after Ontario announced it would extend COVID-19 vaccine intervals in response to the recommendation from Canada’s National Advisory Committee on Immunization (NACI).
In new guidelines posted on the NACI website on March 3, the committee said “current evidence suggests high vaccine effectiveness against symptomatic disease and hospitalization for several weeks after the first dose, including among older populations.”
A spokesperson for Ontario Health Minister Christine Elliott said the news was “welcomed.”
“This will allow Ontario to rapidly accelerate its vaccine rollout and get as many vaccines into arms as quickly as possible and, in doing so, provide more protection to more people,” Alexandra Hilkene said in a statement on March 3.
According to sources, the letter was sent to Canada’s Chief Public Health Officer Dr. Theresa Tam, as well the governments of Ontario, Alberta and British Columbia — all of which have indicated they are planning on implementing the four-month delay.
The draft also raised significant worries about variant spread and the effect a delayed second dose could have.
“What will the impact be on the variants of concern and potential others? This will remain a guessing game without being able to transfer knowledge from properly performed trials,” the letter read.
The doctors urged governments to identify priority populations to receive second doses sooner.
“At a minimum, there should be stratification for the second dose, where the elderly, immunocompromised and individuals in high-risk groups are given the second dose according to the recommended schedule (21-28 days after the first dose).”
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Brad Wouters, the executive vice president of science and research at UHN, said he didn’t send the letter. However, he said he reviewed it and noted it was written by a number of immunologists who have “important concerns” involving the risk.
“They’re really seeking some answers and some of the understanding of the decisions that NACI has made around this recommendation,” he said.
Wouters said he didn’t think UHN was going to take a formal position on the matter, but emphasized it’s important to hear from experts.
“My own position on this is that we have very good evidence from well-conducted phase three clinical trials around the efficacy of these vaccines, that they are incredibly effective under the conditions that they are used,” Wouters said.
“Canada’s really the only country that has gone to a change to four months, you already are in a bit of unknown territory, and what has been done at NACI there’s a panel of experts who are offering their opinions on the expectations of what that risk looks like versus the clear benefit of getting more vaccines to more people earlier.”
When asked about the letter on Tuesday, Tam said officials have been looking at an increasing amount of real-time vaccine efficacy data from across Canada and the world.
She said they are actively studying at the immune response two months and counting after the first dose is administered and noted the effectiveness is still high.
“So if that level of immunity is not expected to suddenly drop, increasing the flexibility of the ability of the provinces to deliver that first dose, which is really safe and effective, to as many people as possible to prevent deaths and hospitalizations is paramount at a point in time where … we’re in a bit of a delicate situation where the epidemiology is that we still have thousands of cases a day, hospitalizations and deaths,” Tam said.
“This was felt to be the most important objective.”
She also emphasized that the NACI recommendation at this point is a maximum interval and with four vaccines now approved to be used in Canada, the second doses could come sooner than four months.
Tam said physicians and scientists will continue to actively monitor rapidly evolving data.
— with files from Hannah Jackson, Megan King and The Canadian Press
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