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Covid-19: Does the vaccine reduce the risk of coronavirus infection?

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Men vaccinated in LA

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According to some studies, people who are completely vaccinated with covid-19 are much less likely to infect others, despite the arrival of the delta variant.Findings refute the prevailing idea in some circles that vaccines no longer do much To prevent the spread of the coronavirus..

“They absolutely reduce infections,” he says. Christopher Byron Brook At the University of Illinois at Urbana-Champaign. “Vaccinated people can get the virus, but the data are very clear and the risk of infection for vaccinated people is much lower than for unvaccinated people.”

A recent study found that vaccinated people were infected with the delta mutant. 63% less likely to infect people Those who have not been vaccinated.

This is only slightly lower Alpha variantBrechje de Gier of the Dutch Center for Infectious Disease Epidemiology and Surveillance, which led the study, said. Her team previously found that people who were vaccinated with alpha were 73% less likely to be infected with people who were not vaccinated.

According to de Gier, what is important to achieve is The full effect of the vaccine on reducing infection Most vaccinated people are not infected in the first place, so it is even higher than 63 percent.

De Gier and her team used data from the Dutch contact tracing system to calculate the so-called secondary incidence (the percentage of contacts infected with positive cases). We then adjusted factors such as age to calculate how much this was reduced by vaccination.

De Gier says that it is not possible to calculate a complete reduction in infection by vaccination because it does not know exactly how much the risk of infection will be reduced by vaccination. However, even assuming that vaccination only halves the risk of infection, this means that the vaccine reduces infection by more than 80% overall.

Others have had the full effect. Earlier this year, Yale University’s Ottavia Prunas applied two different models to Israeli data in which the Pfizer vaccine was used.The conclusion of her team Overall vaccine efficacy against infection was 89%..

However, the data used was only until March 24, before Delta became dominant. The team is currently using the latest data to unravel the impact of Delta, says Purnas.

The idea that vaccines are no longer so effective against infections July news report Infected vaccinated people claim that they can carry as many viruses as others. But even if this is true, vaccines will significantly reduce infections by reducing them in the first place.

actually, Research that triggered news coverage Instead of directly measuring someone’s virus count, they relied on the so-called Ct score, which is a measure of viral RNA. However, this RNA may come from a virus that has been destroyed by the immune system. “You can measure RNA, but it’s useless,” says Timothy Pett of Oxford University.

Currently, there is some evidence that Ct scores are not a good measure of the amount of virus someone has. First, the fact that infected vaccinated people are much less likely to infect others. Peto used UK contact tracing data to conduct a similar study to deGier. Similar results were obtained..

Second, Peto’s team demonstrated that there is little relationship between Ct scores and infectivity. “People who were positive after vaccination seemed to have the same viral load as those who were not vaccinated. We thought they were equally infectious. It turns out to be low, “says Peto. “It’s very important. People were overly pessimistic.”

Yet another piece of evidence comes from a study by Brooke. After the initial positive test, his team took samples from 23 people daily until the infection was resolved and tested the cells in the dish, including infecting the samples.

Five of the six fully vaccinated individuals, unlike most unvaccinated individuals, were not infectious in any of the samples.Studies show that Vaccinated people release less virus and stop releasing it sooner Brooke says more than unvaccinated people.

One of the bad news is that Peto’s research shows the protection that vaccines provide to infected people who infect others. Will it decline over time?, About a quarter three months after the second vaccination. “This made me believe in boosters,” he says. “Given we are in the midst of an outbreak, they should continue to do so. [in the UK].. “

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Covid-19: Does the vaccine reduce the risk of coronavirus infection?

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