Alberta seniors Paddie Walmsley and her husband got their first shot of the AstraZeneca COVID-19 vaccine earlier this month soon after the province started offering the limited doses to Albertans in the age group of 60 to 64 years old.
While the couple is feeling relieved and lucky, they are also anxious about the long wait until July before they can get their second dose.
“It is concerning. We would feel better protected and more confident if we were able to get the second dose sooner than the four months,” said Walmsley, a 60-year-old from Coaldale, a town about 230 km south of Calgary.
On March 3, Canada’s National Advisory Committee on Immunization (NACI) updated its guidelines, recommending provinces and territories extend the time between first and second COVID-19 vaccine doses to four months, from the originally mandated span of three to four weeks, amid vaccine shortages.
NACI said extending the dosing interval will help “opportunities for protection of the entire adult population within a short timeframe.”
But many experts say that elderly adults, as well as the vulnerable population, who have a weaker immune response, should be exempted from this rule.
“Older people… have the weakest immune systems amongst us and COVID-19 preys on that,” said Samir Sinha, director of geriatrics at Sinai Health and University Health Network hospitals in Toronto.
“This ‘one size fits all’ approach to delaying the second dose of the vaccine by up to 16 weeks may not be right for everyone.”
The concerns stem from growing data coming out of the United Kingdom – where both the Pfizer and AstraZeneca vaccines are being given 12 weeks apart – that suggests that the second dose is crucial to get the full benefit of the vaccine for the elderly population.
Looking at the scientific evidence, the first dose wanes much faster compared to the two doses, said Jorgan Fritz, an immunologist at McGill University.
The waning is “clearly high” in the elderly and immunosuppressed individuals, he told Global News.
“The worry of the scientific community is that we are vaccinating without creating an efficacious immune response by doing this increased spacing of the two doses,” Fritz said.
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Vaccine manufacturers Pfizer and Moderna propose intervals of 21 and 28 days, respectively. The protocol for giving the booster shot set and used in the clinical trials for AstraZeneca was one month after the first dose.
In a statement to Global News, Health Canada said: “NACI is aware of early emerging evidence for variable immune responses among immunosuppressed individuals.”
In the coming weeks, the committee will review the extended interval strategy, it added.
Derek Phillips, an 82-year-old from Toronto, Ont., got his first dose of the Moderna vaccine at Seneca College last Saturday.
He said he was taken aback when he was told his appointment for the second dose would be after 14 weeks and not four weeks as indicated on the pamphlet from the provincial health department.
When he questioned the change in the timeline, a woman at the vaccination site said ‘we might call you earlier,’ Phillips said. His main concern is getting the “optimum medical benefit.”
“I don’t think there should be any uncertainty,” the dual U.K.-Canadian citizen added.
“That doesn’t make sense.”
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Tania Watts, an immunologist and professor at the University of Toronto, said the delay in those aged 80 and above is “more risky” than the delay for younger people.
“So while everyone benefits from boosting the immune system with a second dose, the delay is more serious in those at greater risk, such as cancer patients, older people, the immunocompromised,” she told Global News.
Meanwhile, reinfection of COVID-19, although rare, is a concern for seniors.
A large-scale peer-reviewed study published in the Lancet medical journal on March 17 found that most people who have had COVID-19 are protected from catching it again for at least six months, but elderly patients above 65 are more prone to reinfection than younger people.
Earlier in March, an outbreak at a Gatineau, Que., long-term care home, where 96 per cent of the residents and 41 per cent of staff had been vaccinated with a first dose, killed five residents.
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In Canada, the 60-plus population accounts for more than 95 per cent of COVID-19 deaths.
“If the goal is to save the most lives possible, then we would consider shortening that second interval,” said Sinha.
In addition to a tight adherence to the dose regimen recommended and used in clinical trials by the vaccine makers, Fritz said the elderly and vulnerable people should also get a booster shot starting in November to ensure “best immune protection” for the winter.
“There is the fear that a suboptimal immune response could lead to increased occurrence of viral variants,” he said.
— With files from Global News’ Linda Boyle and Su-Ling Goh
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