Link between AstraZeneca vaccine and blood clots clear: European Medicines Agency official

There is a causal link between the coronavirus vaccine developed by AstraZeneca and very rare cases of blood clots, although it remains unclear what the connection is and the possible causes are likewise still unknown, a senior European Medicines Agency (EMA) expert told an Italian on Tuesday.

"It is clear that an association exists" between the vaccine and the dozens of reported blood clots, said Marco Cavaleri, head of the EMA's health threats and vaccines strategy.

"Such cases are extremely rare, and the benefits (of the vaccine) still largely outweigh the risks," he stressed.

"Yet, it is becoming increasingly hard to say there is no cause-effect relationship between the vaccination with AstraZeneca and very rare cases of unusual blood clots associated with a low number of platelets," he said.

In its latest assessment of embolic and thrombotic events reported after coronavirus vaccination published on March 24, the EMA looked at 258 such cases (45 of them fatal) that occurred in Europe out of almost 20 million first doses of the vaccine administered, the Xinhua news agency reported.

On March 31, the agency explained that such an assessment did not unveil "any specific risk factors, such as age, gender or a previous medical history of clotting disorders for these very rare events."

"A causal link with the vaccine is not proven but is possible, and further analysis is continuing," it added.

Cavaleri told the Italian newspaper on Tuesday that the assessment process was "far from over."

The EMA is expected to provide a new evaluation on the use of the AstraZeneca vaccine soon, perhaps by late Wednesday, the European Union's (EU) Health Commissioner Stella Kyriakides said on Twitter on Tuesday.

Meanwhile, the Italian Medicines Agency (AIFA) and the Health Ministry were also due to discuss the issue late on Tuesday, although the AIFA would reportedly not issue any new rule on the AstraZeneca vaccine's use pending the EMA's decision.

Like other EU countries, Italy on March 15 issued a "temporary and precautionary" ban on the use of the AstraZeneca vaccine following reports of a small number of clot deaths in the country.

Three days later, it resumed use of the AstraZeneca vaccine following the EMA's announcement that it was safe.

Also in March, the Italian branch of AstraZeneca said that "an analysis of safety data on over ten million doses administered has shown no evidence of an increased risk of pulmonary embolism or deep vein thrombosis in any age group, gender or batch."

However, an official from the World Health Organization (WHO) said on Tuesday that there was "no link for the moment" between the AstraZeneca vaccine and blood clots, stressing that the benefits of the vaccine were "largely still positive" compared to its risks.

"We continue to see a number of events that are rare events. ... There's no evidence that the benefit-risk assessment for the vaccine needs to be changed," said Rogerio Pinto de Sa Gaspar, Director of Regulation and Pre-qualification of WHO, at a press conference.

The AstraZeneca vaccine was authorized for use in Italy on January 29 and is one of four vaccines currently approved against the coronavirus here, the others being those by Pfizer/BioNTech, Moderna and Johnson & Johnson.

Italy's vaccination campaign is ongoing but it has been marred by a slow start and delays.

To date, the country has administered 11.3 million doses out of the 14.1 million doses available, according to the government. Over 3.5 million people have received both vaccine doses.

At a global level, 269 candidate vaccines are still being developed -- 85 of them in clinical trials -- in several countries including Germany, China, Britain, Russia and the US, according to data released by the World Health Organization on April 2.