Since the beginning of November, about 59% of adult Danes between the ages of 17 and 72 have been infected with covid-19.
This is the latest estimate from the Statens Serum Institut (SSI), which in collaboration with the country’s blood banks has just presented the results for the third round of the blood donor survey.
In the third round, which covers week 7, blood was tested from a total of 5,310 donors. They had blood drawn from the 14th to the 20th. February.
“The proportion with antibodies from covid-19 infection has increased by 15 percentage points since the previous round in week 5. This is far more than between the first round in week 3 and the second round. Here, the share rose by only 6.7 percentage points. ”
“The study also shows that the regional differences are now much smaller and largely evened out since the monitoring began. This reflects that there has been a lot of infection throughout the country, ”says Professor Christian Erikstrup from Aarhus University Hospital.
Finally, the study shows that the dark figure, just like in the previous round of the study, is about one third. And this despite the fact that the infection in the community has increased significantly.
“Data confirms that the increasing population immunity plays a significant role in the fall in the infection we see in all parts of the country right now – and which must therefore be expected to continue”, says CEO Henrik Ullum from SSI.
SSI emphasizes, however, that the calculations are subject to considerable uncertainty.
In part, the study is only based on infection among 17-72-year-old otherwise healthy Danes. In part, the calculations are based on the assumption that the infection among donors is the same as among non-donors.
However, data are very important for predicting future developments. And we would like to thank the blood donors and blood banks for their continued help in providing an overview of the epidemic, ”says Henrik Ullum.
The monitoring of SARS-CoV-2 infections in Denmark is based on positive PCR and antigen tests. In this way, however, not everyone infected in this country can be caught. There will therefore be an under-registration.
To follow how many Danes are infected during the Omikron wave, SSI has therefore initiated a collaboration with the Danish blood banks. Here, donor blood is tested for antibodies to SARS-CoV-2. In this way, one can estimate how many have recently been infected.
The blood is tested for anti-nucleocapsid IgG antibodies. These antibodies are formed only after being infected and not after vaccination. And the IgG antibody level drops after a few months.
Monitoring runs every two weeks until the end of spring 2022.