Highest rate of Covid-19 antibodies identified at ski resort

A study of residents in the Alpine ski resort of Ischgl, the site of Austria’s biggest coronavirus outbreak, found 42% had antibodies for the virus, the highest rate ever proven, the university that carried out the study said on Thursday.

Thousands of people were infected at the resort, which marketed itself as the “Ibiza of the Alps”, as the virus found a breeding ground in crowded apres-ski bars early in Austria’s outbreak.

The first positive test result in Ischgl was on March 7, days after Iceland alerted the Austrian authorities to several of its nationals who it believed caught the virus there. A quarantine was declared a week later but tourists were allowed to leave, further spreading the virus across Europe.

“The seroprevalence of study participants from Ischgl is 42.4%,” the director of the Medical University of Innsbruck’s Institute of Virology, Dorothee von Laer, who led the study, said in a statement by the university.

“We are dealing in Ischgl with the highest seroprevalence ever proven in a study.

Even though at that rate herd immunity cannot be assumed, Ischgl’s population should be protected [from the virus] to a large extent,” she said.

Seroprevalence is the number of people in a population who test positive for a specific disease based on blood serum specimens.

Other studies had found antibody rates of 10% in Geneva and 27% in Italy’s Alpine valley of Val Gardena, the university said.

Antibody and regular socalled PCR tests were carried out on 1,473 people, or 79% of Ischgl’s inhabitants, between April 21 and 27.

Only 15% of those found to have antibodies had previously tested positive for the virus, the university said.

Despite the Ischgl outbreak, Austria has one of Western Europe’s lowest infection rates. It introduced a national lockdown in mid-March, which flattened its curve of infections, and it started loosening that lockdown a month later.

Cases are increasing by fewer than 100 a day and there have been 698 deaths so far.

EVEN THOUGH AT THAT RATE, HERD IMMUNITY CANNOT BE ASSUMED, ISCHGL’S POPULATION SHOULD BE PROTECTED TO A LARGE EXTENT