The Centers for Disease Control and Prevention (CDC) recommended last week that Americans should choose to receive one of the two mRNA-based Covid-19 vaccines over Johnson & Johnson's single-dose shot, due to concerns about blood-clotting side effects. A panel of advisors to the CDC says that Moderna and Pfizer-BioNTech vaccines should now be the preferred choice for most adults.
“Today’s updated recommendation emphasizes CDC’s commitment to provide real-time scientific information to the American public. I continue to encourage all Americans to get vaccinated and boosted,” CDC director Rochelle Walensky said in a statement.
While both men and women reported the clotting side effect, the highest reporting rates were women in their 30s and 40s. The agency’s vaccine panel voted unanimously on December 16 to change its official recommendations.
Before making their decision, the CDC's Advisory Committee on Immunization Practices reviewed the latest data about a rare blood clotting syndrome called thrombosis with thrombocytopenia, which has been linked to the Johnson & Johnson’s Covid-19 vaccine. Since the J&J vaccine became available in 2020, around 16 million Americans have gotten the jab, according to CNN’s Maggie Fox. A total of 54 J&J recipients have been hospitalized, and nine people have died—seven women and two men. Though there are only a handful of cases of blood clotting for every million people vaccinated, the panel concluded the risk was too high.
Symptoms of blood clotting symptoms usually show up around nine days after vaccination, and most patients were hospitalized about five days later, reports Hannah Seo for Popular Science. After two weeks, people who received the J&J Covid-19 shot were unlikely to develop blood clots.
Members of the panel also noted that J&J's vaccine is less effective in preventing Covid-19 than the other two authorized vaccines. Because the vaccine is a single dose that can be stored at higher temperatures than the mRNA vaccines, it has been praised for its usefulness in high-risk and hard-to-reach populations, reports Michael Erman for Reuters.
There are still cases when the Johnson & Johnson vaccine may still be preferable. Young men at risk for the rare heart condition myocarditis, which has been linked to mRNA vaccines, might still opt for the J&J jab.
In a statement Thursday, the CDC said that mRNA vaccine supply was abundant and “given the current state of the pandemic both here and around the world....receiving any vaccine is better than being unvaccinated.” The agency added that the Johnson & Johnson shot will still be available to anyone who is “unable or unwilling to receive an mRNA vaccine.”