On May 5th, the Food and Drug Administration (FDA) placed new restrictions on the Johnson & Johnson coronavirus vaccine. The announcement comes as a result of the J&J vaccine being associated with a rare but potentially deadly blood clotting and bleeding syndrome named thrombosis with thrombocytopenia syndrome (TTS). The condition appears within one to two weeks of vaccination. Even with quick treatment, affected individuals can rapidly worsen and experience long-term health consequences.

The agency said that the risk of the disorder outweighed the benefits of the vaccine for people who are 18 or older and can get another shot. The agency further said that only those who can’t receive other vaccines because they aren’t accessible, clinically appropriate, or refuse to get a different vaccine should receive the J&J shot.

Back in December, officials at the Centers for Disease Control and Prevention (CDC) suggested that other vaccines should be used instead of the J&J one due to preliminary findings. Recent additional analysis prompted the FDA to change the emergency use authorization on how the vaccine can be used, which was granted in February 2021.

The J&J vaccine was somewhat less effective in its clinical trials than the messenger RNA vaccines from Pfizer-BioNTech and Moderna that were authorized in 2020. However, since it was a single shot, officials hoped that it would ease the logistics of vaccination campaigns. About 18.7 million doses of the J&J vaccine have been given in the US, whereas 340.6 million and 217.5 million doses of Pfizer-BioNTech and Moderna have been given, respectively.

The rollout of the Johnson & Johnson vaccines has been slow because it was paused in April 2021 after it came to light some individuals were developing the rare blood clotting condition. Eventually, the campaign was restarted, but manufacturing and supply issues further hindered the rollout.

An updated analysis of safety data through March 18th of this year discovered that there have been 60 confirmed cases of the blood-clotting syndrome, including nine deaths. The FDA said there were 3.23 cases of the clotting syndrome per million doses of vaccine administered and 0.48 deaths per million doses of vaccine administered.

Regulators had hoped to find a way to determine who was most likely to develop the disorder after receiving the vaccine and avoid giving them the shot. The condition has been reported in males and females in a wide age range. The group with the highest rate was women between 30-49 years old. Interestingly, the complication seems much less likely to occur in people 65 and older.