The study published on Friday is the first to directly compare the immune responses of the Pfizer vaccine from the three-week dosing interval tested in clinical trials, and the extended 12-week interval recommended by UK authorities to give at least a few more vulnerable people. protection quickly.
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After Britain decided to extend the interval between doses, Pfizer and its vaccine partner BioNTech said there was no data to support the decision. However, Pfizer said public health considerations outside of clinical trials could be taken into account.
Canada has taken a similar approach, focusing on giving a first dose to as many people as possible before giving a second, thereby extending the time between doses.
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“Our study demonstrates that peak antibody responses after the second Pfizer vaccine are markedly improved in the elderly when this is delayed to 12 weeks,” said Helen Parry, study author based at the University of Birmingham.
Britain started rolling out Pfizer’s vaccine before changing dosing policy, meaning a small number of people who were vaccinated early received the second vaccine three weeks later.
The study, which has not yet been peer reviewed, involved 175 people aged 80 to 99 and found that extending the second dose interval to 12 weeks increased the peak antibody response 3.5 times compared to those who had had it at three weeks. .
Antibodies are part of the immune system, and vaccines also generate T cells. Peak T cell responses were highest in the group with a 3-week interval between doses, and the authors cautioned against shooting conclusions about how protected individuals were based on the dosing regimen they were receiving.
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However, taken with data showing good protection against hospitalization and death from a single injection of Pfizer vaccine, Public Health England said the study was further evidence in favor of the UK approach.
“The UK approach to delaying this second dose has really paid off,” Gayatri Amirthalingam, consultant epidemiologist at Public Health England, told reporters.
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