People in their early sixties, the age group that was given the AstraZeneca vaccine, have fewer antibodies against coronavirus than other vaccinated groups, according to national blood bank Sanquin.

‘It seems as if this vaccine does not give such high levels of antibodies as the mRNA vaccines,’ Zaaijer told TV talk show Op1.

A study of around 1,400 samples from blood donors found that people in the 18 to 25 age group had on average eight times as many antibodies as people aged 61 to 65. People in the 71 to 75 age group had twice as many antibodies, even though they had received their vaccines earlier.

AstraZeneca was the Dutch government’s original vaccine of choice, but it was suspended and then limited to people over 60 because of a small risk of severe blood clotting.

The vaccine fell out of use in the Netherlands over the summer as the government focused on the mRNA vaccines produced by Pfizer and Moderna. The health ministry said in July it would be donating its surplus stocks of AstraZeneca to countries in Africa.

People who had received one dose were given the option of taking the Pfizer for their second jab. The European Medicines Agency, based in Amsterdam, ruled in May that the AstraZeneca vaccine is safe and the benefits outweigh the risks.