“Our position has not changed,” said Emer Cooke, executive director of the EMA, giving an update on the agency’s investigation into cases of the rare clotting disorder cerebral venous sinus thrombosis (CVST) in people vaccinated with Astrazeneca plc’s COVID-19 vaccine. “There is no evidence to support restricting use of the vaccine in any population,” she said.

The update followed a meeting of the EMA’s safety committee on March 31 and after the EMA convened an ad hoc expert group on March 29 to provide further input into the investigation of the serious adverse events.

Independent external experts, including hematologists, neurologists and epidemiologists, discussed possible mechanisms, underlying risk factors and what additional data are needed to understand if there is any causal link between the Astrazeneca vaccine and cases of CVST.

As things stand, the EMA has not identified any specific risk factors, such as age, gender or a previous medical history of clotting disorders. A causal link with the vaccine is not proven, but is possible and further analysis is continuing, Cooke said.

For now, the EMA is of the view that the benefits of the Astrazeneca vaccine in preventing COVID-19, with its associated risk of hospitalization and death, outweigh the risks of side effects.

Countries in Europe, including France, Spain, Germany and Italy, previously said the Astrazeneca vaccine should not be given to people over 65, because there was insufficient clinical trial data to show it was effective in that age group. With 31 of the CVST cases the EMA is investigating occurring in Germany, the government there now says the vaccine should only be given to the over 60s.

The EMA has looked at 62 cases of CVST reported up to March 22, among 9.2 million people who received the vaccine; there are more cases to consider as the review continues, with a final report due next week.

The majority of reported cases of CVST have been in women under the age of 50. Any link with the Astrazeneca vaccine is hard to detect because CVST in the general population occurs in a 10-to-1 ratio in women vs. men, and in the general population it is more prevalent in the 30 to 45 year age group. In the EU, the ratio of people who received the Astrazeneca vaccine is 2-to-1 women to men, and the women who have been vaccinated tend to be younger.