My COVID-19 vaccination

In Germany vaccination against COVID-19 has been going slowly compared to some other places. One of the leading vaccines was developed by Biontech, a company based in Mainz, which is where I live. Due to this and my impression that that vaccine is very good my first choice would have been to get the Biontech vaccine. In the end things turned out differently. The Biontech vaccine is the one which has been given most often in Germany but the number of vaccinations have been limited by the available supply. The vaccine developed by AstraZenenca has also been used here but has acquired a bad reputation. There were several reasons for that. One is the bad relations of the company to the media. Another is the occurrence of rare side effects involving thromboses. A third is that the publicly quoted efficiency of preventing the illness is much less for AstraZeneca than for Biontech (80% compared to 95%). A fourth is that the waiting time between the first and second injections is longer for AstraZeneca (12 instead of 6 weeks). Despite these things my wife and I decided to get vaccinated with the product from AstraZeneca and had our first injections today. Here I want to explain why we did so and discuss some more general related issues.

I already mentioned that AstraZeneca became unpopular. In connection with the thromboses it was only recommended by the Paul Ehrlich Institute (the official body for such things in Germany) for people over sixty. The argument was that since people over sixty had a higher probability of serious consequences if they got infected the net benefit was positive for them. Doctors were having problems getting rid of their doses. However the situation is very dynamic. Although AstraZeneca is still not recommended for people under 60 (like myself) and it is not administered to them in the official vaccination centres doctors (GP’s and specialists) are allowed to vaccinate people under 60 with that product if they inform them about the risks. They are also allowed to reduce the waiting time between the injections. These political moves have led to many people (particularly young people) wanting to get vaccinated with AstraZeneca. The result is that now instead of being hard to get rid of the AstraZeneca vaccine is scarce. Thus now there is a lot of competition and the whole process is quite chaotic. We were lucky that my wife was offered a vaccination with AstraZeneca at a time when this seemed like asking for a favour rather than offering to do a favour. She asked if I could also be vaccinated by the same doctor and got a positive answer. This was our good fortune.

It was still not clear to us whether we should accept the offer. It is in the nature of the situation that many things concerning the disease and the vaccination are simply not known. On the other hand the amount of information available is huge. All this makes a rational decision difficult. From my point of view the thromboses were so rare that they did not influence my decision at all. The combination of the earlier availability of AstraZeneca for us with the longer waiting time meant that it was not clear which option (taking AstraZeneca now or waiting for Biontech) would lead to being fully immunized sooner. We did not want to shorten the interval for the AstraZeneca vaccination (which our doctor would have accepted) for a reason I will discuss later. A reason for making the choice we did was that this gave the feeling of finally making some progress. In the comparison of the efficiencies of the two products it is important to know that if the criterion considered is the risk of serious illness or hospitalization then according to the official figures AstraZeneca is at least as good as Biontech (both at least 95%). In any case, it was a good feeling to know that we had received one dose of the vaccine. A few hours later I have not noticed any side-effects whatsoever.

Let me return to the question of shortening the time between the injections for AstraZeneca. There is some evidence that this decreases the efficiency of the vaccinations and I have read about two possible mechanisms for this which seem to me at least plausible. The first is connected with the phenomenon of affinity maturation. The first B cells which are activated in response to a certain antigen can undergo somewhat random mutations. This means that the population of B cells becomes rather heterogeneous. The different variants then compete with each other in such a way that those which bind most strongly to the antigen come to dominate the population. In this way the quality of the antibodies is increased. If a second vaccination is given too soon it can interrupt the affinity maturation initiated by the first vaccination before the antibodies have been optimized. The second mechanism is as follows. The immune reponse against the antigen remains active for some time after the vaccination. If second vaccination is given while that is still the case then the antibodies generated in the first vaccination can bind to the vector viruses coming from the second vaccination and prevent them from achieving their intended purpose. These are not established facts but I prefer to have plausible hypotheses than a complete lack of a possible explanation.

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