Europe endorses AstraZeneca's COVID-19 vaccine's safety amid blood clot concerns

After a tough few days for the AstraZeneca COVID-19 vaccine rollout, the European Medicines Agency offered fresh backing for the shot’s safety on Thursday. But after reviewing cases of rare blood clots, the agency couldn't definitively rule out the risk.

The regulator reached a “clear scientific conclusion” that the AZ shot is “safe and effective,” EMA executive director Emer Cooke said during a briefing. The protection the shot offers against COVID-19 “outweighs possible risks,” she said.

With thousands dying from COVID-19 in Europe, it's critical to continue vaccinations, Cooke added.

Still, after an urgent review of data after countries stopped vaccinations, the regulator couldn't rule out a possible link to blood clots associated with thrombocytopenia, or low levels of blood platelets. With that potential risk looming, the agency is raising awareness of the issue so doctors and patients know what to look for.

With more awareness, people can “spot and mitigate” any possible side effects, Cooke said. Further, the agency is launching “targeted observational studies” to learn more about the shot.

Around 20 million people have received the vaccine so far, EMA says, and the agency has reviewed seven cases of blood clots in multiple vessels. The agency has reviewed another 18 cases of cerebral venous sinus thrombosis, or clots in the vessels draining blood from the brain.

EMA says a "causal link with the vaccine is not proven, but is possible and deserves further analysis." In the meantime, vaccine recipients should notify their doctor of breathlessness, pain in the chest, swelling or coldness in an arm or leg, persistent bleeding, severe headache or bruising, EMA says.

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EMA’s Thursday endorsement of the vaccine's risk-benefit profile came after similar proclamations from authorities at the World Health Organization and the U.K.’s Medicines and Healthcare products Regulatory Agency. 

Earlier this week, numerous countries in Europe and beyond stopped using the vaccine amid a series of reports of blood clots following vaccination. 

AstraZeneca has stood by the vaccine, saying patient safety is the company’s “highest priority.” 

RELATED: AstraZeneca's touting COVID vaccine safety record, but countries are still dropping out—and supply problems persist 

"Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine, and that includes COVID-19 Vaccine AstraZeneca," a spokeswoman said. "The safety of the vaccine has been extensively studied in Phase III clinical trials and peer-reviewed data confirms the vaccine has been generally well tolerated." 

Aside from the safety worries, the company is also hitting supply hurdles. In recent days, the company cut its European first-half supply target to 100 million doses—down from 300 million earlier. With that supply cut, Europe is now leaning more on the Pfizer/BioNTech shot.