An ongoing study out of the University of British Columbia is raising new questions about the timeline for getting elderly people their second dose of COVID-19 vaccine.
The research, which has yet to be peer reviewed, found that the Pfizer-BioNTech vaccine produced a much weaker antibody result in long-term care residents than it did in younger, healthier people.
“That is a bit concerning, of course, because the dosing interval in some Canadian provinces has been extended, which probably makes sense for younger people and it’s had a good real-world impact because we’re seeing fewer impacts in long-term care,” research team lead Dr. Marc Romney, a clinical associate professor at UBC, told Global News.
“But my concern is that it still leaves them a bit vulnerable, this extended dosing interval, especially if there are elderly frail people in the community, who have probably a similar immune response, and who may think they have high levels of immunity after a single dose.”
Romney said the growing spread of COVID-19 variants and uncertainty about their susceptibility to vaccines only made the issue a more pressing concern.
British Columbia announced it would extend the gap between first and second doses to four months on March 1. The National Advisory Committee on Immunization (NACI), the federal body that advises how vaccines be deployed, later adopted the same position.
In the study, researchers looked at 12 long-term care residents and compared results with 18 long-term care workers.
Romney said both the quantity of antibodies and their effectiveness at blocking the infection and binding to the virus were lower among the long-term care residents.
While the findings are still preliminary and the research sample size was small, Romney said he felt the findings were important enough that they be made public, so that they could help inform decision-making in the province.
“Is it a one-size-fits-all approach, or does it need to be modified for certain vulnerable populations?” Romney asked. “Our data suggests it’s more the latter.”
At her Thursday briefing, provincial health officer Dr. Bonnie Henry said the province was aware of the study, and was watching vaccine effectiveness among seniors and the immunocompromised “carefully.”
The medical community is still learning about COVID-19 and the effects of vaccines, she said.
But real-world data collected in B.C.’s long-term care facilities on vaccine effectiveness has been extremely encouraging she said.
“That is some of the data that allowed us to extend that interval and to recognize that were were getting good protection that was lasting for many weeks,” Henry said.
“We will be continuing to watch, and if we start to see a decrease in real-world protection, in vaccine effectiveness in elderly people then we will speed up second doses.”
On Thursday, NACI said it was reviewing the study, along with findings from studies in Quebec and the United Kingdom.
The committee said based on the data it would consider if exceptions to the longer interval are necessary, but noted that vaccinating more people at a population level remained crucial to reducing overall transmission.
Romney said the study remains underway and will involve testing the same elderly participants to see how long their antibodies last. They will then be followed after they get their second shot to study the effects.
— With files from the Canadian Press
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