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The Covid-19 epidemic is coming down. And the majority of the adult Danish population may have been infected during the large wave of infections with the omicron variant.

Image by fernando zhiminaicela from Pixabay

This is the conclusion of the sixth and final round of the blood donor study, which the Statens Serum Institut (SSI) has carried out together with the country’s blood banks.

Since the beginning of the year, and at two-week intervals, the blood from the country’s blood donors has been tested for antibodies to SARS-CoV-2. In this way, it has been possible to estimate how many people have been infected in Denmark during the omikron wave.

See the results of the 6th round of the survey .

From 14% to 68%

The first round of the study covered the period from November 1 last year to January 4, 2022. Here, the blood from a total of 4,722 blood donors aged 17-72 were examined for antibodies to covid-19.

Based on the results, it was estimated that 14% of Danes aged 17-72 could have been infected with covid-19 from November 2021 to the beginning of January 2022.

The last round of the study covered until March 15, 2022, and here the blood from 6,605 blood donors was examined.

This time, the estimated proportion who may have been infected with covid-19 since early November has risen to 68%. That is 6 percentage points more than the previous round of the survey (week 11).

“In terms of covid-19, Denmark is therefore in a good place right now, where the vaccines and the many covid-19 infections have created a solid immunity in the population,” says SSI’s director Henrik Ullum about the latest results of the study.

Highest in North Jutland

If you dive into the five regions in Denmark, you can see that the proportion of blood donors who have been infected is highest in the North Jutland Region with 74% infected. Conversely, it is lowest in Region Zealand with 61% infected.

There is also still a marked difference in the proportion of infected people in different age groups. The proportion is highest (74-75%) among the younger (17-45-year-olds) and lower (59%) among the older (the 46-72-year-olds).

Useful tool

Now the blood donor survey is over, and at SSI, director Henrik Ullum is happy to have been able to use the blood donors as part of the covid-19 monitoring.

“It has proven to be a very useful tool to follow the epidemic. Especially when the test strategy has changed along the way, and one could fear that fewer were tested. We have already in the measurement from week 9 – three weeks after the wave peaked in week 3 – been able to come up with a fairly accurate estimate of how many have been infected during the omikron wave “, says Henrik Ullum. He sends a special thank you to the blood donors:

“We would not have been able to do this without them, and therefore thank the blood donors many times for being involved,” he concludes.