At the end of November 2020, AstraZeneca delivered good news: the drug manufacturer had ready its corona vaccine Vaxzevria, which was on average 70 percent effective. However, this did not immediately lead to a big cheer, because a week earlier, competitors Pfizer-BioNTech and Moderna had also announced that their vaccines were ready, with an effectiveness of 90 percent and more. “For example, the perception from the start was that the mRNA vaccines from Pfizer and Moderna worked better than the vector vaccine from AstraZeneca. And that was not just perception: the mRNA vaccines dominate corona,” says virologist and vaccine specialist Johan Neyts (KU Leuven).
“Only the risk groups are still being vaccinated in a targeted manner. If you can only offer a vaccine with a lower efficacy than the competition, it will be difficult”
Isabel Leroux-Roels
Head of the Center for Vaccinology at UZ Ghent
And so almost three and a half years later, AstraZeneca reports that it is withdrawing its vaccine worldwide. “Since multiple, varied Covid-19 vaccines have been developed, there has been a surplus of available updated vaccines,” it said in a statement. Demand for Vaxzevria, which is no longer made or supplied, had therefore fallen. The European Union decided to no longer purchase the vaccine before the summer of 2021. In countries with no or less access to mRNA vaccines, including India, it was in use for longer.
Lower efficacy
According to Neyts and fellow professor Isabel Leroux-Roels, head of the Center for Vaccinology at Ghent University Hospital, this choice to withdraw is logical. “The demand for corona vaccines has fallen anyway because there are no longer large-scale vaccination campaigns,” says Leroux-Roels. “Only the risk groups are still being vaccinated in a targeted manner. If you can only offer a vaccine with a lower efficacy than the competition, things will become difficult. In addition, the AstraZeneca vaccine has an extremely rare but very serious side effect. As a result, the balance sheet is somewhat unfavorable all in all.”
Professor Isabel Leroux-Roels explains that it is unnecessary to worry regarding side effects of the AstraZeneca vaccine: “If they occur, they will happen a few days to a maximum of six weeks following the administration of the vaccine.” — © Fred Debrock
By the side effect, Leroux-Roels refers to the thrombosis with thrombocytopenia (TTS) that Vaxzevria causes in very exceptional cases (ranging from one in 40,000 to one in 250,000, depending on the age group). According to the Federal Agency for Medicines and Health Products (FAGG), two compatriots died from the side effect. In the United Kingdom, where AstraZeneca was used even more widely, this would involve 81 people. There is also an ongoing collective lawsuit from relatives of people who died from the vaccine and are demanding compensation.
Some media reported at the end of April that AstraZeneca had admitted for the first time in the context of the trial that Vaxzevria “can cause TTS in very rare cases”, but that is an exaggeration. AstraZeneca already adjusted the package leaflet of the vaccine in April 2021. “I can testify firsthand that the company took this side effect very seriously from the beginning,” says Leroux-Roels.
No problem
The admittedly low risk of TTS was in any case enough to give the image of the AstraZeneca vaccine a second dent. When asked whether that risk might not have been avoided if there had not been such a rush to develop the vaccines at the time, Leroux-Roels is resolute: “No, that might not have been avoided. Clinical studies are conducted on 30,000 to 40,000 people, while it was much less common. You can only notice such rare side effects when a vaccine or medicine is already on the market.”
Anyone who has ever been vaccinated with Vaxzevria should certainly no longer worry regarding the side effects today. “If side effects occur, they will happen a few days to a maximum of six weeks following administration of the vaccine,” said Leroux-Roels. AstraZeneca itself says it is proud that the vaccine has saved “more than 6.5 million lives, according to independent estimates”.