Fully vaccinated people have an approximately 50-60% reduced risk of infection with the Delta coronavirus variant, including those who are asymptomatic, a large UK coronavirus prevalence study revealed on Wednesday.
Researchers at Imperial College London said people who said they had received two doses of the vaccine were half as likely to test positive for COVID-19, taking other factors such as age into account. whether or not those tested have symptoms of COVID-19.
The estimates, which did not break down efficacy by vaccine, are lower than those reported by Public Health England for injections from Pfizer and AstraZeneca.
The researchers said this was neither surprising nor worrying, given that the PHE estimates were based on those who show symptoms and get tested, while the Imperial study is designed to collect more people.
“We are examining efficacy against infection among a random sample of the general population, which includes asymptomatic individuals,” Imperial epidemiologist Paul Elliot, who leads the study, told reporters, adding that even those with symptoms in the study might not have gotten tested otherwise.
“So again, it’s a different group of people. “
The study found that the link between infections and hospitalizations, which had previously weakened, had started to reconverge, a development that coincided with the spread of Delta among young people who may not be fully vaccinated.
The researchers said that overall, the prevalence in unvaccinated people was 1.21%, three times higher than the prevalence of 0.40% in fully vaccinated people, and the viral load in people with COVID was also lower in those vaccinated.
The researchers presented the latest findings from the Imperial’s REACT-1 prevalence survey, which showed the number of infections quadrupled in one month to 1 in 160 people in England.
The latest survey, conducted between June 24 and July 12, covers the period leading up to a peak in infections reported daily on July 17 and found the rise was being fueled by the spread among young people.
Imperial Professor Steven Riley said 5-24 year olds account for 50% of all infections, even though they only make up 25% of the population.
Schools are now closed for summer vacation, and cases have fallen from that peak despite legal restrictions on coronaviruses ending July 19.
“We have shown that before the recent decline, young people were the source of infections,” Riley told reporters.
“This data supports the idea that there is uncertainty as to what might happen in September when schools return and we have increased the indoor mix, due to the infection patterns that we have seen driving growth. “