A registered pharmacy technician prepares a syringe with a dose of a COVID-19 vaccine, in Toronto, on Dec. 22, 2020Melissa Tait/The Globe and Mail
A single dose of Pfizer and BioNTech’s COVID-19 vaccine cuts the number of asymptomatic infections and could significantly reduce the risk of transmission of the virus, results of a British study found on Friday.
Researchers analyzed results from thousands of COVID-19 tests carried out each week as part of hospital screenings of health care staff in Cambridge, eastern England.
“Our findings show a dramatic reduction in the rate of positive screening tests among asymptomatic health care workers after a single dose of the Pfizer-BioNTech vaccine,” said Nick Jones, an infectious diseases specialist at Cambridge University Hospital, who co-led the study.
After separating the test results from unvaccinated and vaccinated staff, Dr. Jones’s team found that 0.80 per cent tests from unvaccinated health care workers were positive.
This compared with 0.37 per cent of tests from staff less than 12 days postvaccination – when the vaccine’s protective effect is not yet fully established – and 0.20 per cent of tests from staff at 12 days or more postvaccination.
The study and its results have yet to be independently peer-reviewed by other scientists, but were published online as a preprint on Friday.
This suggests a fourfold decrease in the risk of asymptomatic COVID-19 infection amongst health care workers who have been vaccinated for more than 12 days, and 75-per-cent protection, said Mike Weekes, an infectious disease specialist at Cambridge University’s department of medicine, who co-led the study.
The level of asymptomatic infection was also halved in those vaccinated for less than 12 days, he said.
Britain has been rolling out vaccinations with both the Pfizer COVID-19 shot and one from AstraZeneca since late December, 2020.
“This is great news – the Pfizer vaccine not only provides protection against becoming ill from SARS-CoV-2, but also helps prevent infection, reducing the potential for the virus to be passed on to others,” Dr. Weeks said. “But we have to remember that the vaccine doesn’t give complete protection for everyone.”
Key real-world data published on Wednesday from Israel, which has conducted one of the world’s fastest rollouts of Pfizer’s COVID-19 vaccine, showed that two doses of the Pfizer shot cut symptomatic COVID-19 cases by 94 per cent across all age groups, and severe illnesses by nearly as much.
The first big real-world study of the Pfizer/BioNTech vaccine to be independently reviewed shows the shot is highly effective at preventing COVID-19, in a potentially landmark moment for countries desperate to end lockdowns and reopen economies.
Reuters
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