VIENNA — A study of residents in the ski resort of Ischgl, the site of Austria's worst coronavirus outbreak, found that at least 8 months after contracting the virus, the vast majority of people remained immune, scientists who conducted it said on Thursday.
The findings provide more insight into how long immunity lasts after infection, and also suggest that herd immunity may start to kick in earlier than widely believed, the team behind the study said.
Austria's main public health agency AGES believes the Ischgl outbreak, in which thousands of people from across Europe were infected, began in February last year, before the first cases in Austria were detected.
The Medical University of Innsbruck conducted a study in April that found 42 percent of Ischgl's population had antibodies for the virus. A follow-up study conducted in November and published on Thursday found the vast majority of those who had antibodies in the first study still had them in the second.
"In close to 90 percent of those who tested seropositive in April, antibodies could also be detected in November," virologist Dorothee van Laer, one of the scientists who carried out the study, said in a statement. The study involved just over 900 people, 801 of whom took part in the first one.
"Despite a slight fall in the concentration of antibodies we can... say that immunity is relatively stable," she added.
The university said its study was one of the biggest of its kind and over one of the longest periods, helping to answer the question of how long immunity lasts after infection.
It also suggests herd immunity starts to kick in sooner than many have suggested, since Ischgl had a much smaller second wave of infections in November than comparable towns in the region.
"It seems that this immunity situation, which was somewhere between 40 and 50% (of the population) in November ... actually protected the population from infection," van Laer told a news conference, adding that basic social distancing measures were in place then, like face masks being required and bars being shut.
(Reporting by Francois Murphy)