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Vaccination in a London club (photo taken on August 8th)
Photo: Alberto Pezzali / AP
According to a British study, two vaccine doses from Biontech / Pfizer or AstraZeneca offer good protection against the delta variant of the coronavirus.
However, the study also suggests that vaccinated people, if they become infected, may have a similarly high viral load as those who were not vaccinated.
When the alpha variant prevailed in Great Britain, the viral load was significantly lower in people who became infected despite a vaccination, says study leader Sarah Walker, professor of medical statistics and epidemiology at Oxford University
Comparison of Alpha and Delta
For the study, which has not yet been reviewed by independent experts, the researchers analyzed a total of results from more than three million nasal and throat swabs from adults in Great Britain - these took place at set times, i.e. regardless of whether someone typical Covid-19 Had symptoms. Asymptomatic cases can also be found using this procedure. To compare the time periods before and after Delta spread, the researchers analyzed about 2.58 million smears from around 380,000 adults between early December and mid-May, and 810,000 test results from 360,000 participants between mid-May and early August.
The scientists came to the conclusion that the protection against infection detected by PCR 90 days after the second vaccination with Biontech / Pfizer was 75 percent and with AstraZeneca 61 percent.
Two weeks after the second dose, this was still 85 percent and 68 percent, respectively.
"These data tell us nothing about the level of protection against serious illnesses and hospital stays, two very important factors when you consider the effectiveness of the vaccines," says Koen Pouwels, who was also involved in the study.
The team was also unable to estimate the effectiveness of the vaccination in the group of older people aged 65 and over because very few of the study participants in this age group in the UK have been unvaccinated since May.
The researchers point out that the study alone cannot clarify whether the similarly high viral load also means that those who have been vaccinated are as contagious as those who are not.
"A larger proportion of the viruses might not be able to multiply in the vaccinated people, and / or the viral load could fall faster in them, as a study with hospital patients suggests," they write.
Nevertheless, this could have an impact on all measures that are assumed to have a low risk of further transmission by vaccinated people.
wbr / Reuters