Concerns of blood clots are rising in multiple countries.

While the United States relies on the Pfizer, Moderna, and Johnson & Johnson COVID-19 vaccines, other countries’ pharmaceutical companies have developed their own vaccines to combat the pandemic. One of the major candidates was developed in tandem by pharmaceutical company AstraZeneca and the University of Oxford and approved for emergency usage in the European Union, but since last week, countries have begun suspending its usage due to health concerns.

Germany, France, Italy, Ireland and the Netherlands have voted to suspend the use of the AstraZeneca vaccine due to reports of inoculated patients developing potentially dangerous blood clots. Both the World Health Organization and the health department of the United Nations have downplayed these concerns, saying that no concrete correlation between the vaccines and blood clots has been determined. Nevertheless, multiple vaccine regulatory bodies from multiple countries have begun calling for in-depth investigations into the shots.

“A careful review of all available safety data of more than 17 million people vaccinated in the European Union (EU) and UK with COVID-19 Vaccine AstraZeneca has shown no evidence of an increased risk of pulmonary embolism, deep vein thrombosis (DVT) or thrombocytopenia, in any defined age group, gender, batch or in any particular country,” AstraZeneca said in a statement.

“There is no causal effect established or anything like that yet, but as a precautionary move in line with the precautionary principle and in an abundance of caution, our clinical advice was to pause the program whilst the EMA does a review of this,” Irish Prime Minister Micheal Martin told CNBC. “This is an unwelcome pause but nevertheless I think it’s important that we take heed of the advice we have received.”

“Covid definitely causes coagulation disorders and each of the vaccines prevents Covid disease, including more severe cases,” said Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine.

“Therefore, it is extremely likely that the benefit of the vaccine notably outweighs any risk for coagulation disorders and the vaccine prevents other consequences of Covid including deaths from other causes.”