Blood clots higher among Covid cases than AstraZeneca recipients, study shows

A preliminary study of more than a million vaccinated people has found that the incidence of rare blood clots was far higher among people with Covid than those who received the AstraZeneca vaccine.

The pre-print study, published in the Lancet, assessed the incidence rates of blood clotting disorders including the very rare thrombosis with thrombocytopenia (TTS) following vaccination with either the Pfizer/BioNTech or AstraZeneca vaccine. This was then compared with the expected “background” rates in a general population, and then against the statistics for people with Covid.

Scientists concluded that both vaccines had “similar safety profiles” and that “regardless of the vaccine used, the increase in rates of thrombosis among persons with Covid-19 is far higher than those seen among persons vaccinated.”

The findings, which have not been peer-reviewed, are an encouraging step for AstraZeneca’s viral vector vaccine, which has been plagued with concerns over incidents of rare blood clots since March.

The study has also left British politicians fuming over what an Italian official described as a “political” move by EU countries including France, Spain and Germany to suspend the British-made vaccine after concerns were raised about the vaccine’s link to rare blood clots.

One government official told Politico’s London Playbook: “The European leaders who trashed the AstraZeneca vaccine have blood on their hands. We now know what we all suspected is true, that they did it out of spite for Britain because of Brexit.”

“When the history books are written, they’ll say these people were directly responsible for the deaths of thousands in developing countries who won’t take AZ because of their anti-vaxx scare stories.”

The findings contrast with a study of 5.4 million people in Scotland, published last month, which suggests that the AstraZeneca vaccine is associated with a small increased risk of immune thrombocytopenic purpura (ITP).

The authors of the study, published in Nature Medicine, stressed that the condition is treatable and that the benefits of vaccination greatly outweigh the risks. They said the same risk was not found for the Pfizer-BioNTech vaccine. 

Researchers said that the increased chance of developing ITP after receiving the vaccine remained smaller than the risk of developing it because of Covid-19 and should not deter the rollout of the vaccine programme.