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The presence of antibodies differs between regions and between groups in society. Among the blood donors screened by the Swedish Public Health Agency, seven percent had antibodies. The authority has also analyzed blood samples from outpatient care, where the same figure was 6 percent.
The Swedish Public Health Agency has analyzed 400 blood donor samples per week between week 17 and week 24. The samples have been taken from nine different regions of Sweden, including Stockholm, Västra Götaland and Skåne.
During these weeks, the presence of antibodies has gradually increased. In Stockholm, the incidence is higher than in the country as a whole, where 12 percent of blood donors had antibodies. In Skåne, the same figure is just under four percent. Younger adults have a higher proportion of antibodies and people over 65 have a lower incidence.
The study shows that the antibodies are more likely to be carried by those who live in a household with more than five people or those who have a profession with many social contacts. However, people who were born in a country other than Sweden or who work in schools and preschools are not more likely to have antibodies.
It’s just this sorts of comparisons for which antibody tests can be used, says Karin Tegmark Wisell, department head at the Swedish Public Health Agency. However, they say little about immunity in society.
– We know that antibodies do not reflect everyone who has actually had the disease. It has been shown in several studies that some do not develop antibodies that can be detected in the blood and that they can also weaken over time. So we cannot draw any conclusions about whether immunity is high or low in society, but we can only relate to its appearance, he said at Thursday’s press conference.
A study from the Karolinska Institute and Karolinska University Hospital shows that some people who have been infected with COVID-19 and had mild or no symptoms develop T cells that provide protection against reinfection of the virus, but not antibodies.
The researchers estimate in the study that about twice as many have developed T cells against the new coronavirus compared to those with measurable levels of antibodies.
It has not been possible analyze blood samples examined so far by the Public Health Agency for T cells. But the authority is now planning more comprehensive surveys of how many have had COVID-19 in Sweden and is working to establish that kind of method. These tests can be done on T cells.
– T cell samples will not be available to the general public this fall, as we see it. But on the other hand, in studies and surveys, you can talk about it, says Karin Tegmark Wisell.
Since the spread of the infection is significantly less now than before in Sweden, the presence of antibodies will likely decrease in the future, according to Karin Tegmark Wisell.
– We know that antibodies break down after a while. If you then have a lesser spread of infection, there will be fewer people carrying antibodies.
Although antibodies appear say relatively little about immunity in society, the Public Health Agency believes that testing is still valuable for them.
– For the individual, it can be of great value. If you belong to a risk group or have relatives who are risk groups, for example. Another situation is for those who work in health and care and get a little runny nose or similar. If you later learn that you have already had the disease, there is no reason to get tested again.
The antibody study conducted by the Swedish Public Health Agency is based on blood tests from week 24, that is, 12 weeks back in time. But development during these weeks shouldn’t have been so good, says Karin Tegmark Wisell.
– We know that there is now a low spread of infection, so we have no reason to believe that there has been a decisive change since the last week of the survey 24.
