Aug. 5, 2021 -- Fully vaccinated people still face considerable risks for contracting COVID-19, according to a new study published Wednesday by Imperial College London.

At the same time, they were three times less likely to test positive for the coronavirus than unvaccinated people.

“These findings confirm our previous data showing that both doses of a vaccine offer good protection against getting infected,” Paul Elliott, director of the survey program and a professor at Imperial’s School of Public Health, said in a statement.

“However, we can also see that there is still a risk of infection, as no vaccine is 100% effective, and we know that some double vaccinated people can still become ill from the virus,” he said. “So even with the easing of restrictions, we should still act with caution to help protect one another and curb the rate of infections.”

The latest findings, which come from an ongoing study of the U.K. population, were based on more than 98,000 swabs taken between June 24 and July 12.

During that time, about 1 in 158 people, or .63%, were infected with COVID-19. This represented a four-fold increase from early June and appeared similar to the numbers seen in October 2020 to January 2021. Among the 254 samples that were sequenced, the Delta variant accounted for 100%, as compared with 80% in the previous report in June.

Unvaccinated people had a three-fold higher prevalence of COVID-19 than vaccinated people. The prevalence rate was 1.21% among unvaccinated people, as compared with .4% in fully vaccinated people. Both groups had more than a five-fold increase in infections from the previous report in June.

Based on the numbers, the researchers estimated that fully vaccinated people in this testing group had a 50% to 60% reduced risk of infection, including asymptomatic cases, as compared with unvaccinated people.

“The Delta variant is known to be highly infectious, and as a result, we can see from our data and others’ that breakthrough infections are happening in fully vaccinated people,” Steven Riley, a professor of infectious disease dynamic at Imperial, said in the statement.

“We need to better understand how infectious fully vaccinated people who become infected are, as this will help to better predict the situation in the coming months,” he said.