A slew of countries decided to halt or delay their rollout of the AstraZeneca COVID-19 vaccine over the past week. The countries’ actions are related to several reports of people who developed blood clots after receiving the shots. But major health organizations say there is likely no link between the vaccine and these health issues—and the benefits of getting vaccinated still outweigh the risks.
Last week, health authorities in Denmark announced on Twitter that the country would be pausing vaccinations with the AstraZeneca vaccine for two weeks due to reports about blood clots. And countries such as Ireland, the Netherlands, Norway, France, Thailand, Indonesia, Bulgaria, Estonia, Lithuania, Austria, and Latvia also said they would be holding off while authorities investigate the issue, Al Jazeera reports. As of this writing, Germany is the latest country to announce it will hold off out of an abundance of caution, Reuters reports.
The AstraZeneca vaccine, which was developed with a team at Oxford University and hasn’t been authorized yet in the U.S., uses an inactivated version of an adenovirus to create a protective immune response in the body. It hasn’t been through the Food and Drug Administration’s emergency use authorization process yet, but in clinical trials the vaccine shows promise in preventing symptomatic COVID-19 infections, hospitalizations, and deaths. There’s also some evidence to suggest it can help prevent transmission of the virus.
But after reports that people developed blood clots (including one person who died in Denmark), some authorities felt it was necessary to pause and investigate as a precaution. Blood clots are “gel-like” clumps of blood that can form in your veins, the Mayo Clinic says. They can can lead to conditions such as deep vein thrombosis, pulmonary embolism, and strokes. To investigate a possible link, researchers will need to compare the amount of people who developed blood clots after receiving the vaccine to the normal rate of people who develop blood clots without the vaccine.
So far, preliminary data from the European Medicines Agency (EMA) EudraVigilance program does not suggest there is a causal relationship between the vaccine and blood clots, the EMA said in a recent statement, meaning that the vaccine is not likely to have directly caused the clots. And the EMA and the World Health Organization (WHO) say that it’s okay to keep giving people the vaccine while they are continuing to monitor for blood clots.
“There is currently no indication that vaccination has caused these conditions, which are not listed as side effects with this vaccine,” the EMA said. “The number of thromboembolic events [blood clots] in vaccinated people is no higher than the number seen in the general population. As of 10 March 2021, 30 cases of thromboembolic events had been reported among close to 5 million people vaccinated with COVID-19 Vaccine AstraZeneca in the European Economic Area.” Ultimately, the EMA’s Pharmacovigilance Risk Assessment Committee concluded that “the vaccine’s benefits continue to outweigh its risks and the vaccine can continue to be administered while investigation of cases of thromboembolic events is ongoing.”
Out of 17 million people vaccinated in the U.K. and E.U., there have been 15 cases of deep vein thrombosis and 22 cases of pulmonary embolism. “This is much lower than would be expected to occur naturally in a general population of this size and is similar across other licensed COVID-19 vaccines,” AstraZeneca said in a statement. Data from AstraZeneca’s clinical trials, which involved more than 60,000 people, also did not suggest a link between the vaccine and blood clots, the company said.
It’s not clear when countries will decide they have sufficient evidence to resume the AstraZeneca vaccinations. Thankfully, at this point, many countries have multiple COVID-19 vaccine options available, including the Pfizer/BioNTech and Moderna mRNA vaccines as well as the Johnson & Johnson vaccine. But that’s certainly not true everywhere. Considering just how crucial these vaccines are in our efforts to stop the spread of COVID-19, having more options is definitely better.