People who have been fully vaccinated against it Covid-19, are much less likely to infect others with coronavirus, despite the prevalence of the Delta variant, according to a new Dutch scientific study. The findings disprove some claims that vaccines - in addition to protecting the vaccinated themselves - do not prevent the pandemic from spreading.
The Dutch researchers, led by Dr. Brechje de Gier of the Dutch Center for Infectious Diseases and Infectious Diseases Surveillance, who made the relevant publication in medRxiv, according to "New Scientist", estimated that vaccinated people infected with breakthrough infections) are 63% less likely to transmit the coronavirus to unvaccinated people. The study compared the diagnosed cases Covid-19 in households where their members had been vaccinated or were still unvaccinated.
The same research team had previously found that fully vaccinated people infected with the Alpha variant (predominant before Delta until a few months ago) were 73% less likely to infect others. Therefore, the appearance of Delta has only a small negative effect - of the order of 10% - in reducing the effectiveness of vaccines, in terms of preventing the transmission of the virus to third parties.
The Dutch scientists pointed out that in fact the full effect of vaccines on reducing transmission is greater than 63%, because most fully vaccinated people not only do not get sick with Covid-19, but are not even infected with the coronavirus. De Gier said it was not possible to accurately estimate the full positive impact of vaccines on reducing the spread of the virus, because it is not known exactly how much vaccination reduces the risk of infecting a vaccinated person. Assuming the reduction is about 50% (ie a vaccinated person is half as likely to be infected with a coronavirus as an unvaccinated person), then it is estimated that vaccines reduce transmission by more than 80% overall.
"Vaccines clearly reduce transmission," said Dr. Christopher Byron Brook of the University of Illinois at Urbana-Champaign. "Vaccinated people do transmit the virus in some cases, but the evidence is clear that the risk of transmission for a vaccinated person is much, much lower than for an unvaccinated person."
A study led by him showed that, after infection, vaccinated people eliminate less coronavirus from their body and in addition stop doing so earlier than unvaccinated people who become infected.
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