An evaluation by the German Society for Neurology confirms: Sinus vein thromboses are more common after vaccination with AstraZeneca than after vaccination with the mRNA vaccines from BioNTech and Moderna. It was noticeable that the risk is increased not only in younger but also in older women. This finding could have an impact on the future vaccination strategy. However, the researchers emphasize that the overall risk is very low and the benefits of the vaccinations far outweigh them.
The vaccine ChAdOx1 from AstraZeneca has been criticized because, in very rare cases, it can cause thrombosis in the sinus and cerebral veins as a serious side effect. These thromboses, in which the blood flow from the brain is disturbed, can lead to serious neurological damage and strokes. After the first cases became known, Germany temporarily suspended vaccinations with AstraZeneca and then changed the vaccination recommendation so that only people over 60 years of age receive this vaccine. For this age group, the risk of thrombosis was previously considered to be lower.
Surveyed neurological clinics in Germany
A survey published as a preprint by the German Society for Neurology (DGN) now shows that vaccination with AstraZeneca also carries an increased risk of sinus vein thrombosis for women over 60 years of age. For the study, a team led by Jörg Schulz from RWTH Aachen University asked all neurological clinics in Germany how many cases of cerebral sinus and cerebral vein thrombosis as well as ischemic and hemorrhagic strokes occurred within one month after a Sars-CoV-2 vaccination. A total of 87 reports were received, of which experts confirmed a possible link to the vaccination for 62.
53 of the 62 confirmed cases occurred after vaccination with the AstraZeneca vaccine and nine after vaccination with the BioNTech vaccine. No events have been observed with the Moderna vaccine. However, only 1.2 million doses of this vaccine had been administered by the end of data collection in mid-April, compared to 16.2 million doses of BioNTech and 4.6 million doses of AstraZeneca. Of the confirmed cases, 45 were sinus vein thrombosis (37 after AstraZeneca vaccination, eight after BioNTech vaccination). There were also nine reports of strokes, one after BioNTech vaccination, and four cases of cerebral hemorrhage, all after AstraZeneca vaccination.
Women more affected than men
More than three quarters of the reported side effects occurred in women. Of the 45 people with sinus vein thrombosis, 36 were under 60 years of age. For better comparability, the researchers related the number of cases that occurred to the total number of people of the same sex and age who had received the respective vaccine. So they calculated the event rate per 100,000 person-years. For women under 60 years of age, the event rate for sinus vein thrombosis after administration of the AstraZeneca vaccine was 24.2 per 100,000 people per year, and for men of the same age it was almost three times lower at 8.9 per 100,000. For BioNTech, the rate for under 60s was 3.6 / 100,000 for women and 3.5 / 100,000 for men. Women over 60 years of age had a very low event rate of 0.8 / 100,000 person-years after vaccination with BioNTech; there were no events in men over 60 years of age, regardless of which vaccine they were vaccinated with.
“Until then, we were not surprised by the data,” says co-author Tobias Kurth from Charité University Medicine. “However, we have seen a new safety signal.” Contrary to expectations, the incidence for women over 60 years of age after administration of the AstraZeneca vaccine was 20.5 / 100,000 person-years. “Our data shows that older women also have an increased risk of sinus and cerebral vein thrombosis after being given the AstraZeneca vaccine. Whether this leads to a change in the recommendation for vaccination with ChAdOx1 should be quickly assessed using the available data in a risk-benefit analysis. “
Communicate transparently
According to current knowledge, the cause of the increased risk is a so-called vaccine-induced immunogenic thrombotic thrombocytopenia (VITT). Antibodies are formed against a part of the unspecific immune system, the so-called platelet factor 4 (PF4). Apparently, the PF4 sitting on the blood platelets reacts with components of the vaccine and forms complexes to which the antibodies bind in turn. This leads to clumping and even thrombosis. Exactly which component of the vaccine it is has not yet been clarified.
In view of the many millions of inoculated doses, the number of serious side effects is very low, emphasize the researchers. “When weighing up the fact that the risk of sinus vein thrombosis is increased by a factor of ten in the case of a Covid 19 infection, the disease relatively often leads to thrombotic events resulting in death, and vaccination only extremely rarely,” explains Co -Author Hans Christoph Diener from the University of Duisburg-Essen. DGN President Christian Gerloff also affirmed: “From a global perspective, the benefits of vaccines approved in Germany outweigh the very low risks many times over.”
However, it is important to communicate transparently that older women also have an increased risk of thrombosis after the AstraZeneca vaccination. “We are not questioning the vaccination, nor the AstraZeneca vaccine, but we think that all people, especially women, should be informed about this risk before the vaccination, especially with regard to the symptoms they will experience afterwards have to pay attention. In addition, a new risk-benefit assessment should be carried out very promptly by the responsible authorities, ”said Gerloff.
Source: Jörg Schulz (RWTH Aachen) et al., Preprint, doi: 10.1101 / 2021.04.30.21256383