About 5.5% of Dutch blood donors have corona antibodies

The results of Sanquin's second measurement show that approximately 5.5% (+/- 0.5%) of the Dutch blood donors have developed antibodies against the coronavirus. This is a modest increase compared to the measured 3% in April. This is due to the fact that the Netherlands is now moving towards the end of the outbreak peak and because the lockdown measures ensured a limited spread of the virus. This is the preliminary conclusion that Sanquin draws from this follow-up study.

More than 7,000 donations were tested in the period from 10 to 20 May, 12 weeks after the first known COVID-19 infection in the Netherlands. As with the first measurement, these are blood donors between the ages of 18 and 75 who didn’t show any sign of symptoms for at least two weeks at the time of donation.

Prof. Dr Hans Zaaijer, research leader at Sanquin: “We expected an increase in the percentage, because more donors have now been able to recover from an infection and have been able to donate afterwards. The increase found is relatively small, which is in line with what RIVM showed about the decreasing spread of the infection. The lockdown measures are effective which means that fewer people have become infected.”

Indicative number

Zaaijer: “The 5.5% percentage is indicative because our results have to be confirmed in other research that has not yet been completed. Until those results are known, we have to take into account a margin of error of about half a percent. We are expected to complete the confirmation study in two weeks, and Sanquin can thereafter provide an update per region. ”


Sanquin's research into herd immunity is the first large-scale study in the Netherlands, making the results valuable and transparent. Because only donors are examined, the percentage found is not entirely representative of the Dutch population. Research led by the RIVM is also being conducted, the PIENTER Corona study. Sanquin will contribute to this research by regularly testing over 2000 donors for the presence of antibodies.