Sweden’s Public Health Authority has launched a survey to measure and estimate how many in the community have had COVID-19. Blood samples are collected from laboratories in clinical chemistry and clinical immunology in nine regions: Jämtland, Jönköping, Kalmar, Skåne, Stockholm, Uppsala, Västerbotten, Västra Götaland and Örebro.


The collection takes place during eight weeks in the spring of 2020. A total of 1,200 samples are collected each week for analysis of antibodies. Antibodies show that the immune system recognizes the SARS-CoV-2 virus.

The analyzes for week 18 (a total of 1,104 analyzed samples) show, as expected, the largest proportion of positive antibody tests in Stockholm. A total of 7.3 percent of the blood samples collected from people in Stockholm were positive in the antibody study, which can be compared with a total of 4.2 percent in Skåne and 3.7 percent in Västra Götaland.

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.

Regarding age differences, the results show that COVID-19 antibodies were most common among people between 20 and 64 years. In total, 6.7 percent of the samples in this group were positive, which can be compared with 4.7 percent in the age group 0-19 years and 2.7 percent in the age group 65-95 years.

The antibody analyzes are done in collaboration with SciLifeLab / KTH.

Sweden has reported 33,459 cases and 3998 deaths to date.