The Centers for Disease Control and Prevention (CDC) quickly approved an advisory panel recommendation Thursday that adults receive the Pfizer or Moderna COVID-19 vaccines over the Johnson & Johnson vaccine.

Although 17 million people in the United States have already taken the J&J shot, nine people have died after developing a rare blood clotting disorder called thrombosis with thrombocytopenia, the CDC's Advisory Committee on Immunization Practices said, according to USA Today.

Most people affected by blood clots were 30-to-49-year-old women.

CDC Director Dr. Rochelle Walensky supported the panel's decision several hours later.

“Today’s updated recommendation emphasizes CDC’s commitment to provide real-time scientific information to the American public,” Walensky said, according to The Washington Post.

The single-dose J&J vaccine was seen as a welcome alternative that could be used for people unlikely to come back for a second shot compared to the two-dose Pfizer and Moderna vaccines.

Last week, a non-peer-reviewed study showed that people who have had the J&J vaccine were at a greater risk of developing Guillain-Barré syndrome, a rare but severe autoimmune disorder.