The US health authorities CDC and FDA announced this last weekend. The Janssen vaccine does not structurally cause fewer side effects than that of AstraZeneca. This is the end of the matter with regard to health services: about once in 500,000 times the side effect is more than acceptable to continue using the vaccine, according to the FDA.
The vaccine does, however, receive a warning in the package leaflet: in extremely rare cases it can cause the blood reaction VITT.
The side effects in the US mainly affected young women. Three of them died, seven are still in hospital. In addition, the CDC is investigating a further ten suspected cases of women who became ill after vaccination with the vaccine.
Whether the new finding by the American health authorities has consequences for the Dutch approach is unclear. A spokesperson for the ministry announced on Monday morning that he would come up with a response later.
Just last week, Minister Hugo de Jonge said he saw no reason to restrict the vaccine, like that of AstraZeneca, for certain groups of people. Another factor is that the Janssen vaccine (11.3 million doses ordered) is one of the foundations of the vaccination campaign in adults between 18 and 65 years old.
As with the AstraZeneca vaccine, the side effect appears to be highly dependent on age. According to a table compiled by the CDC, the risk in women in their 30s is about one in a hundred thousand. In people over 50, Americans saw only two cases of the side effect, out of 1.4 million vaccinations. After some 750,000 injections, the side effect was not found even once in people over 65.
Professor of epidemiology and thrombosis expert Frits Rosendaal (LUMC) is not surprised. New cases were expected to come to light in the US, the European medicines authority EMA also said last week. “And this is about the same kind of side effect as we have seen with AstraZeneca. It is not surprising that you can see roughly the same numbers. ‘
German researchers announced last week that they have an idea why the problems arise. The AstraZeneca vaccine contains some residual molecules from the culture process, which can clump with a blood protein called platelet factor-4. In very rare cases, this triggers a chain reaction in which antibodies against these protein clots instruct the blood to form clots.
Since the Janssen vaccine is made in the same way, experts expect that the Dutch vaccine will also cause the side effect in very rare cases.
Incidentally, Rosendaal points out that there may be a factory effect: the side effect seems to occur more in one place than in other places. For example, the side effect at AstraZeneca in India has not yet been established once after 83 million vaccines. This suggests that the vaccines may still be a lot safer with certain adjustments in production.