More than a fifth of blood donors in the Netherlands have developed antibodies against coronavirus, according to the latest analysis by blood bank Sanquin.

The figure of 21% is up from 18.6% in February and 13% in January. The presence of antibodies in a blood sample indicates the donor has developed resistance to the virus, either through infection or vaccination.

Sanquin microbiologist Hans Zaaijer warned that antibodies did not necessarily offer complete protection. ‘Unfortunately we can’t say in general that a person with antibodies is guaranteed to be immune,’ he said.

Sanquin said the figures were ‘strongly indicative’ of the spread of the infection through the Netherlands, given that very few people who are eligible to be donors have been vaccinated.

The blood bank analyses a sample of 2,000 blood donations each week to monitor the progress of resistance to the virus.

In the southern provinces of Noord-Brabant and Limburg 26% of donors were found to have antibodies, while in the rest of the country the level is around 20%. The south of the country was hardest hit during the first wave of coronavirus 12 months ago.

Women are more likely to be resistant to the virus, with 24% of samples containing antibodies compared to just 16% for men. Sanquin said the higher number of women working in healthcare professions may explain the imbalance.