The European Union's drug regulator on Tuesday found a possible link between Johnson & Johnson's (JNJ  ) COVID-19 vaccine and rare blood clots with low blood platelet levels, advising that a warning should be added to the drug's product information. However, the agency reiterated that the benefits of the one-dose vaccine greatly outweigh the potential risks.

In reaching its conclusion, the European Medicines Agency's (EMA) safety committee, known as the Pharmacovigilance Risk Assessment Committee (PRAC), examined all available evidence, which included eight cases of unusual blood clots paired with low levels of blood platelets in the United States. All cases occurred in patients under 60 years of age within three weeks of inoculation, with one of the cases being fatal.

More than 7 million people were vaccinated with the J&J vaccine as of April 13, according to the EMA.

PRAC found that the blood clots occur mostly at unusual sites such as in the veins in the brain, known as cerebral venous sinus thrombosis, and the abdomen, called splanchnic vein thrombosis, and in arteries. The blood clots would be present alongside low levels of blood platelets and sometimes bleeding.

A possible explanation for the rare side effect is that it is an immune response to the vaccine, similar to a condition seen sometimes in patients treated with the drug heparin, according to the EMA. The cases reviewed for the J&J vaccine were similar to cases that occurred following inoculation of the COVID-19 vaccine developed by AstraZeneca (AZN  ) and Oxford University.

"COVID-19 is associated with a risk of hospitalization and death. The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of COVID-19 Vaccine Janssen in preventing COVID-19 outweigh the risks of side effects," the agency said in a press release.

J&J announced on Tuesday that it will resume shipments to the 27-nation bloc following the EMA's review.

In the United States, the one-shot vaccine is still under review after the U.S. Food and Drug Administration's advisory pause earlier this month. The vaccine is expected to resume use in the U.S. with new warnings or restrictions, according to Dr. Anthony Fauci, the nation's lead infectious disease expert and White House chief medical advisor.

"My estimate is that we will continue to use [the J&J vaccine] in some form," Fausi said during an interview with NBC's "Meet the Press" on Sunday. "I doubt very seriously if they just cancel is. I don't think that's going to happen. I do think that there will likely be some sort of warning of restriction or risk assessment."