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The Oxford-AstraZeneca COVID-19 vaccine may be able to reduce transmission of the coronavirus, while stopping serious illness and death from COVID-19, initial data suggests.
This is the first time that a vaccine has shown that it can stop the spread of the virus, according to the BBC. Still, experts warn that more data is needed to confirm this trend.
To examine transmission, researchers at the University of Oxford ran weekly coronavirus tests on British participants enrolled in a vaccine trial and found that the rate of positive results decreased by about 67% after participants have received a dose. A negative test means that no virus is present and reduces the likelihood that a person will be infected, even asymptomatically. People without a detectable virus in their airways cannot spread the virus. The work has not yet been peer reviewed but has been published as a pre-print with the Journal The Lancet.
Related: Quick Guide: COVID-19 Vaccines Used and How They Work
Other vaccine studies, on the other hand, mostly tested people who had symptoms of COVID-19, not everyone signed up for the trial, meaning they couldn’t tell how many people vaccinated were asymptomatic, but still infectious to others.
“If there was no impact of a vaccine on asymptomatic infection, one would expect an effective vaccine to simply convert severe cases to mild cases and mild cases to asymptomatic cases, with the overall PCR positivity unchanged, ”the authors wrote in the study. But that’s not what happened – the total number of positives has gone down.
Experts have been cautious, saying more data is needed before this reduction in transmission is confirmed, according to the New York Times.
And the data from this vaccine cannot be applied to others for COVID-19. However, there are indications that the Moderna vaccine may also reduce transmission; when the participants came for their second dose of this vaccine, they were also tested for SARS-CoV-2 and the rate of asymptomatic cases fell by 60%, according to the Boston Herald.
The AstraZeneca trial investigated whether the vaccine prevented serious illness and death. They found that a single dose of the vaccine was 76% effective in protecting people against symptomatic illness 22 days after vaccination. They also found that the timing of the second dose had a dramatic impact on effectiveness; vaccine efficacy increased from 54.9% when the second dose was given less than six weeks after the first injection to 82.4% when the two doses were given 12 weeks or more apart.
This finding suggests that the dosing interval, and not the dosing level, has the greatest impact on vaccine efficacy, according to a statement. The UK has taken a different approach from other countries by trying to vaccinate as many people as possible with a single dose and delaying the second dose by about 12 weeks, according to the BBC. Some experts have warned that delaying the time between doses, however, could create space for the emergence of new variants, from a JAMA perspective.
The Oxford-AstraZeneca vaccine has been urgently approved in the UK but has not yet been approved in the US One in six people in the UK, or around 10 million, have been vaccinated in the UK with the Pfizer or Oxford-AstraZeneca vaccine. But the UK has also approved the Moderna COVID-19 vaccine and will likely receive doses in the spring, according to the BBC.
Originally posted on Live Science.
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