Updated at 10:50 a.m. ET
Sweden is the latest European country to suspend the administration of a COVID-19 vaccine made by AstraZeneca following reports of abnormal blood clotting in recipients.
Venezuela on Monday announced it wouldn't authorize use of the vaccine in the country at all following those reports.
The Swedish Public Health Agency said early Tuesday that as a precautionary measure it would suspend use of the Oxford-AstraZeneca COVID-19 vaccine until the European Medicines Agency, or EMA, reveals findings from its ongoing investigation into reports of negative side effects in patients.
The country joins several other European nations including France, Germany, the Netherlands and Ireland that suspended administration of the vaccine this week.
In a briefing with reporters on Tuesday, EMA's Executive Director Emer Cooke said the agency was investigating reports of at least 30 cases of unusual blood disorders and would release its findings on Thursday.
"The benefits continue to outweigh the risks, but this is a serious concern and it does need serious and detailed scientific evaluation," Cooke said.
Dr. Peter Arlett, the head of the pharmacovigilance and epidemiology department at EMA, said a causal link between the blood clotting problems and the vaccine had yet to be established and that such cases in vaccine recipients are "very, very rare."
Other European countries such as Italy, Austria, Norway and Denmark suspended, delayed or limited rollout of the vaccine over similar safety concerns.
The World Health Organization continues to support and encourage using the vaccine.
The AstraZeneca vaccine, made in conjunction with the University of Oxford, is not authorized in the United States. It is used widely in Europe.