UBC, SFU study raises questions around timing of Pfizer vaccine doses in seniors

VANCOUVER (NEWS 1130) – While Canada’s expert panel on vaccinations looks into the possibility of giving some people one dose of a COVID-19 vaccine instead of two, new research from a small-scale study shows that might not be enough for some seniors.

Researchers out of the University of British Columbia and Simon Fraser University say at least when it comes to the Pfizer-BioNTech vaccine, a single dose produces a much weaker antibody response in long-term care residents than it does in younger healthy adults.

“Results from this study in long-term care facilities in Vancouver reveal that individuals of advanced age, following the first dose of a two-dose vaccination regimen, are less able to generate as strong an antibody response, both in terms of magnitude and function, compared to adults of younger age,” explained Dr. Marc Romney, clinical associate professor in UBC’s Department of Pathology and Laboratory Medicine, and medical leader for Medical Microbiology and Virology at St. Paul’s Hospital.

“It will be important to assess whether this observation extends to older persons living in the community as this may inform the optimal timing of the second dose for this population,” said Romney, who co-led the study.

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That calls into question the current working theory that it’s okay to wait as many as four months between doses.

But there are some caveats here. It’s unclear if the results would have been the same if seniors not in long-term care facilities were included in the data gathering.

Researchers also admit the study, which was funded by the COVID-19 Immunity Task Force, wasn’t huge — just 18 long-term care residents and 12 younger health-care workers took part. The research also has not been peer-reviewed.

The study collected blood samples in late 2020 and early 2021 from participants after they had received their first dose of the COVID-19 vaccine.

“The antibody response was actively triggered in young, healthy people following a single dose of vaccine, while the response was clearly not as robust in older individuals. This indicates that some older people — not only in long-term care but also in the community — may be incompletely protected after their initial dose,” said Dr. Romney.

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