Oxford University study: with the same viral load, vaccinated infects less
Those who have had the vaccine and are infected with the Delta variant are not as contagious as those who have not been vaccinated, even with the same viral load. This is indicated by a study conducted by researchers at Oxford University and published in pre-print in Medrxiv on September 29, but not yet peer-reviewed.
A previous study had found similar viral loads in vaccinated and unvaccinated individuals infected with Delta, casting doubt on how much vaccination can prevent the transmission of SARS-Cov-2. For the new observational study, which first authored David W. Eyre, the researchers looked at data from 139,164 people who had been vaccinated fully or with just one dose, Pfizer-BioNTech or AstraZeneca vaccines, as well as people who not vaccinated.
Of these, 51,798 tested positive. The data show that those who received the double dose could infect 65% less than an unvaccinated person if they had the Pfizer vaccine and 36% if they had received AstraZeneca.
Furthermore, the vaccinated had less infection even though the viral load in their airways was the same as the unvaccinated (measured by the number of CT cycles needed to detect viral RNA in the molecular swabs). “Vaccination reduces the transmission of the Delta variant,” the researchers conclude, “but less than the Alpha”.
–
