COVID-19 less likely to be spread by vaccinated people, study finds

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A COVID vaccination is administered, 2021 (Nexstar, file)

OXFORD, Eng. (WTVO) – Scientists at the University of Oxford have found that people vaccinated against COVID-19 are less likely to spread the virus if they become infected.

Scientists examined records of 150,000 contacts that had been traced from about 100,000 initial cases, according to NBC News. Samples reportedly included people fully or partially vaccinated, as well as people that were unvaccinated. Scientists looked at how vaccines affected the spread of the virus in people who had a breakthrough infection.

The researchers, who had been looking at the Pfizer and AstraZeneca vaccines, found that both vaccinations reduced transmission of the virus. People were 65% less likely to test positive if the person who they were exposed to had been fully vaccinated with the Pfizer vaccine, while the AstraZeneca vaccine made it 36% less likely. If someone had only received one dose of the vaccine, the risk of transmission was reportedly much higher.

While the study was only posted Thursday and has not yet been peer reviewed, the findings were said to be credible by scientists not associated with the research. One of these doctors was Dr. Aaron Richterman, an infectious disease physician at the University of Pennsylvania.

“It is the highest quality study we have so far on the question of infectiousness of vaccinated people infected with delta,” Richterman said.

A recent study from Singapore found that people who have been vaccinated are likely clearing the virus from their body faster than unvaccinated people, finding that levels of the delta variant in infected people were the same regardless of vaccination status, but that virus levels dropped by day seven in people that had been vaccinated.

However, the study found that protection against transmission in vaccinated people can decrease over time, showing that people who had been fully vaccinated, and had breakthrough cases, were just as likely as unvaccinated people to spread the virus three months after their vaccinations.

Doctors, such as Susan Butler-Wu, a clinical microbiologist at the University of Southern California, said that masks and testing remain important while community transmission remains high.

“We need to combine our vaccines with other measures to reduce how much virus we get exposed to by things like masking and testing,” Butler-Wu said. “Additive measures is the name of the game here.”

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