AstraZeneca seems to be losing efficacy fastest: blood bank

Vaccinated people between the ages of 61 and 65 have a lot fewer antibodies against the coronavirus than vaccinated people in other age groups. Hans Zaaijer, doctor-microbiologist at blood bank Sanquin, said this on talk show Op1 on Tuesday evening. According to Zaaijer, this is the group that received AstraZeneca vaccines through their GP. "It seems that this is a vaccine that produces less good, high antibodies than the mRNA vaccines."

Sanquin examined the number of antibodies in approximately 1,400 vaccinated blood donors. This showed, among other things, that the longer a person has been vaccinated, the lower the antibodies are. According to Zaaijer, the very youngest donors, aged 18 to 25, have on average almost eight times more antibodies in their blood than people in the group aged 61 to 65. An older age group, aged 71 to 75, also has on average twice as many antibodies in their blood, while this group was vaccinated earlier than the 61 to 65-year-olds.

It was previously known that AstraZeneca's coronavirus vaccine, like the Janssen vaccine, can cause a combination of clot formation and a reduced number of platelets in very rare cases. That risky combination is known as thrombosis with thrombocytopenia syndrome (TTS). Both vaccines were administered to people at the start of the vaccination campaign in the Netherlands. 

In the spring, it was decided to mainly use the mRNA vaccines by Pfizer/BioNTech and Moderna. These vaccines do not have the severe side effects mentioned. The AstraZeneca vaccine has not been used in the Netherlands for months. Janssen is still available. The European Medicines Agency still considers both vaccines safe.