LONDON (AP) — The European Medicines Agency is expected to provide updated guidance Friday on how countries across Europe should use the coronavirus vaccine developed by AstraZeneca.

Earlier this month, the Amsterdam-based drug regulator for the 27-nation European Union said there was a “possible link” between the AstraZeneca vaccine and rare blood clotting disorders, but that the benefits of getting the shots outweighed the risks.

The agency's experts have since been considering related issues, including whether people who received a first AstraZeneca dose should be offered a second shot, and if there are specific risk factors that might make some people more vulnerable to developing the unusual blood clots.

The EMA previously described the clots as “very rare” side effects and said the vaccine label's should be modified so doctors and patients are aware.

It’s still unclear how frequently the rare blood clots occur. According to data from the U.K., which has administered more AZ vaccine than any other country, there were 30 such cases among 18 million doses, as of late March.

Last month, more than a dozen countries, mostly in Europe, suspended their use of the AstraZeneca vaccine over the blood clot issue. Most restarted — some with age restrictions — after the EMA said countries should continue using the vaccine.

The agency this week identified a similar possible link between blood clots and the COVID-19 vaccine developed by Johnson & Johnson. As with the AstraZeneca product, the EMA recommended labeling changes but said the benefits of getting vaccinated outweighed the risks.