No increased blood clot risk after second dose of AstraZeneca

New data shows AstraZeneca’s Covid-19 vaccine carries no additional risk of rare blood clotting disorder after the second dose.

A study published in the Lancet medical journal found that the estimated rate of thrombosis with thrombocytopenia syndrome (TTS) in people who had received both doses was 2.3 per million. This figure is comparable to that of the unvaccinated population.

Data taken from the same source indicated a rate of 8.1 per million in people who have had only one dose.

The European Union’s drugs regulator has been investigating cases of TTS since March and has found possible links to Vaxzevria and to Johnson& Johnson’s singe dose Covid-19 shot.

It did not, however, find any additional risks accompanying the second dose.

Safety concerns

The second dose of the Astra vaccine has still raised safety concerns after reports of death in a small number of people who received it. These recorded risks have prompted several European regulators to reserve the vaccine for older adults. Some receivers of the first vaccine chose to switch to another product for their second dose.

According to the Medicines and Healthcare products Regulatory Agency, about 24.7 million first doses and 22.8m second doses had been given in the UK by July 14th. By that point the UK regulators had received 411 reports of rare blood clots with platelets after the the first dose of the vaccine, with 71 death reports. Five of the deaths occurred after the second dose.

Mene Pangalos, Astra’s executive vice president of biopharmaceuticals research and development, said in a statement on Wednesday that “these results support the administration of the two-dose schedule of Vaxzevria”.