About 3 percent of blood donors in the Netherlands have developed antibodies against Covid-19, the respiratory disease caused by the coronavirus, RIVM director Jaap van Dissel told the Tweede Kamer based on an as-yet-unpublished study by blood bank Sanquin, NU.nl reports.

If blood donors are representative of the Dutch population, then around 3 percent of Netherlands residents have had the coronavirus to a more or lesser extent. "This concerns several hundred thousand Dutch people," Van Dissel said during his weekly update on the state of affairs surrounding the coronavirus to parliament.

Sanquin tested blood and plasma samples of Dutch donors to see if they've had the virus. Preliminary results show that the presence of antibodies differs per age group. 3.6 percent of young blood donors between 18 and 20 years old (688 individuals) have Covid-19 antibodies. That percentage decreases as donors get older. No antibodies were found among donors between the ages of 71 and 80, though the number of donors in that age group is also much lower - only 10 individuals.

Van Dissel stressed that the investigation is still ongoing. But this suggests that individuals who have recovered from the coronavirus have "some degree of immunity". The RIVM previously said that people with milder symptoms seem to build up less immunity than people who became very ill from Covid-19.