Here's what Sweden's first coronavirus antibody tests tell us

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Here's what Sweden's first coronavirus antibody tests tell us

Sweden's Public Health Agency has shared the result from its first coronavirus antibody tests.


An antibody test checks the blood for antibodies, which show whether you have previously had an infection. They are different from the general coronavirus tests, which only tell us whether or not you have the infection at that moment. 

Laboratories collected around 1,200 samples per week over an eight week period, in nine of Sweden's regions: Jämtland, Jönköping, Kalmar, Skåne, Stockholm, Uppsala, Västerbotten, Västra Götaland and Örebro.

In the week ending May 3rd, 7.3 percent of the samples from people in Stockholm were positive in the study. That means antibodies were found in their blood, meaning that 7.3 percent of those tested in the capital city had previously been exposed to the coronavirus.


Stockholm had the highest proportion of positive results, which was as expected given that the region has had the highest number of confirmed cases and deaths due to coronavirus. In Skåne, 4.2 percent of samples were positive, compared to 3.7 percent in Västra Götaland.

Although these samples were taken at the end of April, the Public Health Agency said: "The numbers reflect the state of the epidemic earlier in April, as it takes a few weeks for the body's immune system to develop antibodies."

It it is not clear exactly how these numbers line up with the Public Health Agency's earlier model that predicted a quarter of the Stockholm population would have had the virus by May 1st. But state epidemiologist Anders Tegnell said the figures were "not far off" those in the model. 

"We aren't at seven percent [infection rate in Stockholm] now. It was seven percent around week 15, so that is quite a long time ago. These people were immune in week 18 [the week ending May 3rd], that means they fell ill at some point in week 14 or 15. We are somewhere around 20 percent plus in Stockholm now," Tegnell told journalists at the press conference.

It is still unclear what level of immunity previous infection by the virus provides. But several studies have suggested that people who have been infected do have some antibodies that according to the World Health Organisation would likely "provide some level of protection" against re-infection. But there is still no evidence to show whether people are fully immune, or for how long.


"When we come to a level that reduces the spread of infection significantly, that's still something we don't really know and that's why we have never discussed herd immunity as a goal. Rather, the goal is that we have measures in place, that we keep the spread of infection low enough so that healthcare and other [parts of society] can continue to function," Tegnell said.

The tests also showed which demographics had been most affected by the virus.

Across the whole country, antibodies were most common among adults aged between 20 and 64, with 6.7 percent of tests in this age group coming back positive, compared to 4.7 percent positive for the age group 0-19 and just 2.7 for the age group 65-70.

"There's a big difference between different age groups in society which is good. The group over 65 and 70 has managed to isolate themselves, and children have a lower level of illness than the group between 30 and 64," said state epidemiologist Anders Tegnell at Wednesday's press conference. 


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