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Vaccine vials and syringe

CDC: Rare blood clots seen after J&J vaccine; mRNA vaccines preferred

December 17, 2021

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Federal health officials are recommending adults get mRNA COVID-19 vaccines instead of Johnson & Johnson’s (J&J’s) vaccine amid concerns about rare but potentially fatal blood clots.

The Centers for Disease Control and Prevention’s (CDC’s) Advisory Committee on Immunization Practices (ACIP) voted 15-0 in favor of expressing a preference for the Pfizer-BioNTech and Moderna vaccines but stopped short of saying use of the J&J vaccine should be discontinued. CDC Director Rochelle P. Walensky, M.D., M.P.H., signed off shortly after.

“Today’s updated recommendation emphasizes CDC’s commitment to provide real-time scientific information to the American public,” Dr. Walensky said in a statement. “I continue to encourage all Americans to get vaccinated and boosted.”

The committee’s recommendation came just days after the Food and Drug Administration (FDA) announced people who have a history of thrombosis with thrombocytopenia (TTS) should not get the J&J vaccine.  

Health officials paused use of the vaccine for about 10 days in April after reports of severe cerebral venous sinus thrombosis (CVST). While use of the vaccine resumed, they continued monitoring for reports of blood clots and presented new data Thursday.

Those data show there have been 54 cases of TTS after the J&J vaccine, a rate of 3.83 cases per million doses. Cases have been seen in people ages 18-70 years and among both males and females. The highest rates have been among females ages 30-49.  Just over half of the cases have a CVST. While some patients had potential risk factors like obesity and hypertension, 39% had none.

All of the patients with TTS were hospitalized including 36, who were treated in the intensive care unit, according to the CDC. There have been nine deaths ranging in age from 28-62, with a median of 45 years. Each of the people who died had features of severe CVST. The overall death rate is 0.57 per million doses of J&J vaccine and again was highest in females ages 30-49.

ACIP members said Thursday when they lifted the pause on J&J in the spring, there was a shortage of other vaccines.  Now there are plenty of Pfizer-BioNTech and Moderna doses that can be used. Those vaccines have been shown to have higher effectiveness and while there is a small risk of myocarditis, most of those cases have been mild.

While committee members expressed a preference for the mRNA vaccines, some expressed concern discontinuing use of J&J could impact global supply. They also agreed there are certain scenarios in which J&J could still be beneficial, including for people who have had a severe allergic reaction to a previous dose of mRNA vaccine, people who would not get vaccinated otherwise and people who prefer J&J despite the safety concerns. They emphasized the need to educate patients about the risk for TTS.

“There legitimately are some who may opt for the (J&J) vaccine even after being appropriately informed,” said ACIP member Beth P. Bell, M.D., M.P.H., clinical professor in the Department of Global Health at the University of Washington. “And I don’t think that it’s right for us to make that option unavailable to them if in fact that’s what they choose to do.”

When it was first authorized, the single-dose J&J vaccine was seen to be beneficial to populations who may have a hard time returning for a second dose. However, many ACIP members say they now believe a booster is crucial to get better protection.

ACIP members commended safety officials for detecting the TTS cases and taking action.

 “I want to remind everybody this is in part a reflection of the strength of our vaccine safety surveillance system and just remind everyone that safety surveillance continues daily,” said ACIP member Matthew F. Daley, M.D., senior investigator at the Institute for Health Research at Kaiser Permanente Colorado.

Pfizer-BioNTech vaccine safety for ages 5-11 years

The CDC also reviewed safety data on use of the Pfizer-BioNTech vaccine for children ages 5-11, which began in early November. More than 7 million doses had been given to this age group as of Dec. 9. 

Most reactions reported to the v-safe smartphone monitoring system have been mild to moderate, with about 1% of recipients reporting they sought medical care.

There have been 3,233 reports to the Vaccine Adverse Event Reporting System (VAERS), 97% of which have been non-serious.

Two deaths have been reported in young girls, both of whom had complicated medical histories and whom investigators described as fragile. Both cases are still under review.

There have been eight confirmed cases of myocarditis in this age group reported to VAERS and the cases have been mild, according to the CDC.



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