AstraZeneca second jab does not increase risk of blood clots

Incidence of clotting in those twice vaccinated with AstraZeneca is comparable to typical rate

AstraZeneca's vaccine has suffered reputational damage over the blood clotting furore. EPA

A second dose of AstraZeneca's Covid vaccine does not increase the instances of rare blood clots, according to a new study.

Data published in the Lancet medical journal on Wednesday found that the estimated rate of thrombosis with thrombocytopenia syndrome (TTS) after the second dose of the Vaxzevria vaccine, the official name of the vaccine, was 2.3 per million in those inoculated. This is comparable to the typical rate seen in those who have not been vaccinated. The rate after the first dose is 8.1 per million.

The AstraZeneca-led and funded study evaluated reported cases on the drugmaker's global safety database occurring within 14 days of administration of the first or second dose as of April 30.

"Unless TTS was identified after the first dose, these results support the administration of the two-dose schedule of Vaxzevria, as indicated, to help provide protection against Covid-19, including against rising variants of concern," said AstraZeneca senior executive Mene Pangalos.

The Anglo-Swedish company instigated the research after its University of Oxford-engineered shot suffered reputational damage as a result of the clotting furore that led several countries to either ban the shot completely or make it available only to certain demographic cohorts.

It renamed its Covid-19 vaccine Vaxzevria in Europe as the pharmaceutical company struggled to reassure the public that the drug was safe, but the product itself was unchanged.

It has experienced production delays and a threatened European Union lawsuit.

The EU drug regulator in March started investigating cases of clotting and found Vaxzevria and Johnson & Johnson's single-dose shot could potentially be causative. It has, however, maintained that overall benefits of both vaccines outweigh any risks they may pose.

A total of 316 cases of TTS were recorded in adults who received AstraZeneca's vaccine in the European Economic Area, authorities said on May 28.