The European Medicines Agency’s safety committee (PRAC) on Thursday gave a resounding endorsement of the Oxford/AstraZeneca vaccine against COVID-19, concluding that the vaccine’s benefits vaccine “far outweigh” any risks  –  despite a possible link between some vaccinations and rare cases of blood clotting associated with low levels of blood platelets. The EMA statement followed two weeks of mounting concerns over reports of such rare events – leading to 17 countries to suspend the vaccine rollout, at least temporarily. 

In a press briefing Thursday evening, an EMA panel stressed that the AstraZeneca vaccine “is not associated” with an increase in the overall risk of blood clots. Nor is there evidence of problems related to specific batches of the vaccine or to particular manufacturing sites. 

However, the EMA safety review did find that the vaccine may be associated with very rare cases of blood clots associated with thrombocytopenia, i.e. low levels of blood platelets (clotting elements in the blood), and also including rare cases of clots in the vessels draining blood from the brain (CVST).

“The EMA Committee has come to a clear scientific conclusion. This is a safe and effective vaccine. Its benefits in protecting people from COVID-19, with the associated risks of death and hospitalisation, outweigh possible risks,” said EMA Executive Director Emer Cooke at the press briefing, adding that overall, “The committee also concluded that the vaccine is not associated with an increase in overall risk of thromboembolic events or blood clots.” 

At the same time, she said, in the Agency’s Pharmacovigilence Risk Assessment Committee (PRAC) investigation and review, a “small number of cases of rare and unusual, but very serious disorders” were detected, that triggered a more focused review.  “And we still cannot rule out definitively a link between these cases and the vaccine,” said Cooke. 

As a result, she said that the agency would be adding a warning about rare events to the vaccine label and patient information – as well as launching more follow up studies. 

“If it were me, I would want to be vaccinated tomorrow,” Cooke stated, when asked by reporters if she would take the AstraZeneca vaccine herself – or wait for another product. ”But I would want to know if anything happens to me after vaccination, what I should do about it, and that’s what we’re saying today.  

“I want to reiterate that our scientific position is that this vaccine is a safe and effective option to protect citizens against COVID-19. It demonstrated that at least 60% efficacy in clinical trials and preventing coronavirus disease, and in fact the real world evidence suggests that the effectiveness could be even higher than that.”

Blood Clots – Still Very Rare Events 

Cooke stressed that the instances of thrombocytopenia-associated blood clotting remained very rare events. And rare adverse events are common with almost any vaccine or medication:

“About seven million people have now been vaccinated in the EU with the AstraZeneca vaccine, and 11 million have been vaccines in the UK…When you vaccinate millions of people it’s inevitable that you have rare or serious incidents,” she said.

“But I want to reiterate that our scientific position is that this vaccine is a safe and effective option to protect citizens against COVID-19.” 

According to the latest EMA data, of an estimated 20 million people in the United Kingdom and Europe that have so far received the vaccine as of March 16, the EMA had reviewed only 7 cases of blood clots in multiple blood vessels (disseminated intravascular coagulation, DIC) and 18 cases of CVST (cerebral events).

”A causal link with the vaccine is not proven, but is possible and deserves further analysis,” stated an EMA news release issued simultaneously with the press briefing. 

Greater Proportion of Very Rare Cases Observed in Young Women 

A greater proportion of these very rare cases, however, have been observed in young women, the committee members acknowledged. This may also explain why more are being seen on the European continent than in the United Kingdom, where the AstraZeneca rollout focused first on older groups. 

The EMA experts did not rule out, either, a possible link between such rare events and contraceptive pill use, which can increase the overall risk of blood clots for young women: 

“Yes, it is always a distinct possibility,’’ said Sabine Straus, EMA Safety Committee head, in referring to those risk factors that might contribute to such a rare event among those being vaccinated. “One of the risk factors that is highlighted for the [thrombosis] disease or the syndrome, as such, is also oral contraceptives. The committee also is investigating if the risk of such events might be higher among recovered COVID patients who are vaccinated.” 

A past COVID infection might also add to the risks of such, she said. “COVID is an important risk factor for thrombosis and also a post-COVID syndrome. So that might have played a role.” 

She added that smoking was also a general risk factor for thrombosis anyway, but cautioned, “I am not sure it’s a risk factor for these specific cases, but it’s something that we are also looking into.” 

United Kingdom versus Europe Differences 

There have also been proportionately fewer reports of the rare events in the United Kingdom – just three cases – as compared to elsewhere on the European continent, including seven cases in Germany, three in Italy, one in Spain and two in India, the panel stated. 

Said Peter Arlett, head of EMA analytics, “we know that the AZ vaccine in the UK, was given predominantly to older patients, compared to the totality of European member states. And therefore, if blood clot cases are more common in younger women, for example, then it would suggest that you get more cases in Europe than you would in the UK.”

In some European countries, health workers, including young women, have been a first priority in vaccine campaigns.

The panel also said that they would be investigating other reports of other rare adverse events seen in any of the vaccines that have so far been EMA approved. Those have also included reports in the United States of sudden decreases in blood platelet clotting elements, called “immune thrombocytopenia” (ITP), shortly after vaccination with the Pfizer and Moderna vaccines.  The syndrome can cause excessive bruising and bleeding. 

Said Straus, “A separate investigation has been started for ITP, and that is a signal that is ongoing for the moment.” 

Image Credits: HPW .