A panel of outside advisers to the U.S. Centers for Disease Control and Prevention on Thursday voted to recommend that Americans choose one of the other two authorized COVID-19 vaccines over Johnson & Johnson’s shot because of the rare but sometimes fatal cases of blood clotting.
The CDC’s Advisory Committee on Immunization Practices voted unanimously on the recommendation. The regulator still needs to sign off on the guidance.
Cases of thrombosis with thrombocytopenia syndrome (TTS), which involves blood clots accompanied by a low level of platelets, have previously been reported in recipients of the J&J vaccine. The highest reporting rates are in women under 50.
The CDC said that the rate of such incidents is higher than previously estimated in both women and men.
At least nine people have died following the blood clotting incidents in the United States, the CDC has said.
Members of the panel also said J&J’s vaccine is less effective in preventing COVID-19 than the other two authorized vaccines.
In a presentation to the committee, a leading J&J vaccine scientist said the vaccine generates a strong and long-lasting immune response with just a single shot.
“In the setting where many people do not return for a second dose or a booster, the durability of the single-shot Johnson & Johnson vaccine as a primary regimen could make a crucial difference in saving lives in the U.S. and around the globe,” J&J’s Dr. Penny Heaton said in the presentation.
J&J’s vaccine uses a technology based on a modified version of an adenovirus to spur immunity in recipients, while the other two authorized vaccines use messenger RNA technology.
J&J’s one-dose vaccine received emergency use authorization in March. In April, U.S. regulators paused administering the vaccine for 10 days to investigate the blood clotting.
A CDC scientist said on Thursday that the rate of deaths from TTS did not decrease after the pause in April.
Fewer Americans have received the J&J shot than the other two vaccines — by a significant margin. Out of more than 200 million fully vaccinated people in the United States, around 16 million received J&J’s vaccine, according to CDC data.