Delayed second shot raises concerns
Some immunologists in Canada are concerned about the decision to allow as much as a four-month delay between COVID-19 vaccine shots.File photo
By Peter Jackson, Local Journalism Initiative Reporter, The Telegram
March 16, 2021
Rising concerns about COVID-19 variants and a possible third wave of infections across Canada have convinced national and provincial health officials that getting at least one dose of vaccine into more arms is now a top priority.
However, a number of immunologists have questioned a controversial recommendation this month to allow a delay of as much as four months between first and second doses.
Last week, Newfoundland and Labrador’s chief medical officer of health said she changed her mind about delaying the second dose of vaccine for residents based on data coming out of other jurisdictions.
“It was really the new evidence that came forward,” Dr. Janice Fitzgerald told reporters. “It was the evidence that we saw come out of Quebec and out of B.C., as well as what we were seeing in the U.K., really made a difference to the National Advisory Committee on Immunization (NACI) as to what they felt was reasonable to recommend.”
Fitzgerald said her office has always deferred to NACI recommendations.
“Seeing how fast this variant can spread and how quickly things went from being lovely to being way less than lovely, that certainly reinforced to us the importance of having those vulnerable populations vaccinated with at least one dose of a safe and effective vaccine.”
However, NACI admits real-world evidence doesn’t extend as far as four months.
“Recently, real-world vaccine effectiveness data presented to or reviewed by NACI assessing PCR-positive COVID-19 disease and/or infection from Quebec, British Columbia, Israel, the United Kingdom and the United States support good effectiveness (generally 70-80 per cent, depending on the methodology used and outcomes assessed) from a single dose of mRNA vaccines (for up to two months in some studies),” NACI reported in its March 3 recommendation. “While studies have not yet collected four months of data on effectiveness of the first dose, the first two months of population-based effectiveness data are showing sustained and high levels of protection. These data include studies in health-care workers, long-term care residents, elderly populations and the general public.”
Local concerns
On March 6, St. John’s rheumatologist Dr. Majed Khraishi voiced his concerns about the move in a letter to the editor, saying the research NACI is relying on is not yet peer-reviewed and is largely based on incomplete statistical analysis.
“We must remember that the first vaccine available in the West was only approved less than three months ago in the U.K., and there is no widespread experience with these vaccines extending beyond three months at most,” he wrote. “Also noteworthy, the pharmaceutical companies that made these vaccines have clearly stated that there is no evidence available yet to justify changing the current dosing interval recommendations.”
Khraishi is not alone.
A March 8 joint letter to federal health officials by almost a dozen Canadian immunologists — obtained by GlobalNews — says decision-makers are not considering the risks involved in delaying doses longer than any other country has so far recommended.
The letter, signed by senior specialists with major institutions in Ontario and Quebec, was reportedly sent to Canadian Chief Public Health Officer Dr. Theresa Tam and to some provincial leaders.
It outlined possible consequences not being taken into account.
“Scientifically, we can predict many scenarios, one being that a limited T cell response, together with the lack of a neutralizing antibody response, could lead to protection of the individual from severe disease, while permitting this individual to continue to spread the virus, therefore creating a situation where the individual is somewhat protected but not allowing herd immunity,” the authors wrote. “Will this really benefit Canadians, given that a proportion will not take the vaccine?”
Uncertainty about the coronavirus’s ability to spread even in vaccinated people has been highlighted a number of times by Newfoundland health leaders.
Like Khraishi, the authors warn that statistical data on hospitalizations and deaths does not address what might be going on at the molecular level. They even suggest it could foster the mutation of new variants of concern.
“Is it worth setting Canadians off down a path where there will be no way to make future decisions based on the findings of these trials? When will booster doses be given? What will the impact be on the variants of concern and potential others?” they wrote. “This will remain a guessing game without being able to transfer knowledge from properly performed trials.”
The debate had already been simmering in Britain, where officials are now allowing a 12-week interval between shots of the AstraZeneca vaccine.
That’s longer than what even the World Health Organization (WHO) recommends for countries facing “exceptional circumstances.”
In January, the WHO’s recommendation was that the interval between doses may be extended up to 42 days, on the basis of currently available clinical trial data.
Speaking to Global News, Tam said national experts are closely monitoring the immunity the vaccines provide over time, but they have to balance that with the risk of continued spread.
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“(I)ncreasing 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’