The European Medicines Agency (EMA) said Friday that a review of AstraZeneca's coronavirus vaccine found its benefits still outweighed the risks for adults of all age groups, despite possible links to blood clots.

In new guidance, the drug regulator also said that people who had received a first dose of the vaccine should get the second one too. The agency added, however, that it wasn't known whether the risk of clotting after a second dose would change compared to after the first.

The EMA review came after a number of countries, many of them in Europe, limited the use of the vaccine to older age groups after possible links to blood clotting in younger people. Denmark is the only country to stop using the vaccine altogether.

Blood clots in just 1 out of 100,000

"It showed that the benefits of vaccination increase with increasing age and infection rates," the Amsterdam-based EMA said in a statement. Because the elderly are much more likely to suffer a serious bout of COVID-19, the risks posed to them by potential side effects are far smaller, relatively speaking, when weighed against the risk from the virus.

"The benefits of Vaxzevria outweigh its risks in adults of all age groups; however, very rare cases of blood clots with low blood platelets have occurred following vaccination," the EMA said, using the vaccine's brand name.

The statement said the EMA's analysis of Europe-wide AstraZeneca data found that blood clots had been observed in just one out of 100,000 people who received the vaccine. 

Earlier this month, the EMA reported that there was a "possible link'' between the AstraZeneca vaccine and a very rare, but often fatal, form of blood clot affecting the brain. That, along with the pharmaceutical firm's delays in delivering doses to the EU, has affected public confidence in the jab.

The EMA this week also identified a similar link between blood clots and the vaccine from Johnson & Johnson, which uses the same adenovirus vector technology as AstraZeneca.

The regulator said on Tuesday that there had been 287 cases of the rare clots reported worldwide in people who had received the AstraZeneca shot, 25 cases following the BioNTech-Pfizer vaccine, eight after the Johnson & Johnson shot and five after the Moderna jab. It said it had identified a "possible" link but that investigations were ongoing.

nm/msh (Reuters, AFP, AP)