Thirty cases of rare blood clotting have been identified in the recipients of AstraZeneca’s coronavirus vaccine, British regulators said on Thursday.

“Up to and including 24 March, we have received 22 reports of cerebral venous sinus thrombosis (CVST) and 8 reports of other thrombosis events with low platelets, out of a total of 18.1 million doses of COVID-19 Vaccine AstraZeneca given by that date,” the Medicines and Healthcare products Regulatory Agency said.

The agency added that no such reactions were seen in people who got the Pfizer-BioNTech vaccine. “Our rigorous review into the UK reports of rare and specific types of blood clots is ongoing,” it said.

However, the regulator said that the benefits of coronavirus vaccines outweigh any risks and people should continue to get inoculated.

Several countries had suspended the use of the AstraZeneca vaccine last month but later announced that they would resume it after the European medical regulator said the jab was “safe and effective”.

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British Prime Minister Boris Johnson had also vouched for the safety of the vaccine earlier this month. “That vaccine is safe and works extremely well, and now, only six months later, it is being made in multiple places from India to the US, as well as Britain, and it is being used around the world,” he had said.

On March 15, World Health Organization chief scientist Soumya Swaminathan said during a press briefing that no causal link had been established yet between blood clotting and the vaccine. However, some countries expressed doubts about the safety of the shot after several cases emerged of people developing blood clots or brain haemorrhages after inoculation.

AstraZeneca also said earlier in March that a safety review of people inoculated with its coronavirus vaccine had shown no evidence of increased risk of blood clots.

In India, the AstraZeneca-Oxford vaccine is one of the two vaccines approved for emergency use. Covaxin, developed by Bharat Biotech in collaboration with the Indian Council of Medical Research and the National Institute of Virology, is the other vaccine.