Impurities in Astrazeneca vaccine may cause rare side effect

The very rare side effect of the Astrazeneca vaccine, thrombosis in combination with a reduced platelet count, may well be prevented, according to German scientists.

Scientists have found in the vaccine tiny remains of a thousand species of human proteins that do not belong there. By better purification of vaccines, future problems may be avoided, says in a preliminary publication of the scientists that De Volkskrant writes about.

The rare side effect has been reported eight times by Dutch people after vaccination with AstraZeneca. A woman died of a blood clot in the lungs. โ€œIt‘s an interesting idea of what might be going on,โ€ says Anke Huckriede. She is a vaccinologist at the UMC Groningen. โ€œBut,โ€ she says, โ€œit still needs to be explored further. This is not the end of the story.โ€

Huckriede does not surprise the fact that scraps of up to a thousand substances have been found in the vaccine. โ€œThe vaccine is based on human cells. They are encouraged to produce harmless cold viruses that contain the code for the spike protein of the coronavirus. Those viruses are in a liquid on top of the cells. The vaccine is then extracted from it, but the liquid also contains proteins that come from the human cells themselves.โ€

She thinks that a very small number of people can now be sensitive to human proteins. โ€œThe blood then reacts to that and there is a kind of chain reaction in which proteins play a role.โ€

Thrombosis expert Frits Rosendaal of the Leiden UMC says that the possible cause fits in the picture he has of this rare severe thrombosis. โ€œIt’s in line with what we already know.โ€

A platelet actually sacrifices itself, he says. โ€œWhen it comes into contact with unknown dust, it inflates itself as it were, causing a clotting. But you also lose the platelet.โ€

Vaccologist Cรฉcile van Els of RIVM and Utrecht University also thinks that the impurities are a possible explanation for the side effect. โ€œBut there are more options. This week, for example, I came across mouse studies from a number of years ago in the professional literature. This showed that adenoviruses – including those used by Janssen and AstraZeneca in their vaccines – can cause a shortage of platelets in mice.โ€

‘Purification takes time, materials and money’

According to Huckriede, it is technically possible to further purify the vaccines. โ€œBut every step you take means that you can produce less and that manufacturing becomes more expensive. Every step takes time, materials and therefore money.โ€

Rosendaal calls it simplistic to think that the issue is solved โ€œjust for a momentโ€ by better purification. โ€œIn a general sense, that will be possible,โ€ he says. โ€œBut it is not clear which dust should be removed. And when you find the right substance, it needs to be tested on millions of people before you know if it works.โ€

He wonders what remains of the vaccine and whether a new vaccine is actually being developed. โ€œIt seems too time-consuming and too expensive.โ€