That’s the finding of a large new study carried out in the United Kingdom. It determined that there’s a far greater risk of developing blood clots from a COVID-19 infection than from getting a jab of either the AstraZeneca or Pfizer-BioNTech vaccine designed to protect people against the disease.

Only around 66 people out of 10 million who received the first dose of AstraZeneca were at risk for thrombocytopenia—or blood clots in the veins—as opposed to 12,614 people who reported blood clots out of 10 million who tested positive for COVID-19.

The study was run by researchers from University of Oxford who followed a total of 40 million cases of those who received their first doses of AstraZeneca or Pfizer between December 2020 and April 2021, and 1.7 million COVID-19 patients.

The researchers are unaffiliated with the Oxford scientists who worked on the AstraZeneca vaccine. The results were published by the British Medical Journal (BMJ) this week.

‘A net positive’

Public health experts hope the findings will sway the vaccine-hesitant to take up the jabs.

The study confirms “substantially higher and more prolonged risks after infection than after vaccination,” says Olaf H. Klungel, a professor of Pharmacoepidemiologic Methods at Utrecht University who did not work on the study. He added the findings suggest “a net positive benefit-risk balance in favor of vaccination.”

The researchers found that people who contracted the virus were more likely to have lower levels of platelets compared with those who received a first dose of either vaccine. The study also showed the unvaccinated who contracted the disease were at greater risk for a stroke.

The study results are welcome news for AstraZeneca, which, since March, has been enduring a PR crisis after first Denmark then other EU countries halted their use of the vaccine owing to unusual reports of blood clots.

AstraZeneca has since maintained the number of clotting incidents was far fewer than what would occur for people not inoculated.

Amid that uproar, the European Medicines Agency was quick to declare COVID-19 a far greater health risk than the vaccine. Still, doubts lingered over the AstraZeneca shot. Countries, including the U.K., have recommended that healthy adults under the age of 30 be given a different vaccine for their second dose.

The study published by BMJ did not determine whether the identified blood clots were caused by the vaccine.

The findings come as vaccine take-up in the U.S. has faltered while Europe continues to see relatively strong demand. In much of the European Union, tough new measures have pushed the bloc’s inoculation rate well above that of the U.S.