- COVID-19 vaccines from Pfizer and Moderna should be "preferred" over Johnson & Johnson's shot, a U.S. government advisory panel said Thursday after reviewing data on potentially dangerous blood vessel blockages from clotting associated with J&J's vaccine. The recommendation follows a strengthened warning the Food and Drug Administration added to the shot two days ago.
- Cases of the blood vessel blockages prompted U.S. regulators to pause use of the J&J vaccine not long after its emergency authorization in early 2021, as other countries' health agencies did with a similar vaccine developed by AstraZeneca's that's also uncommonly associated with the side effect.
- The recommendation from the Centers for Disease Control and Prevention's advisory panel, confirmed by the agency later Thursday, is likely to further constrain use of J&J's vaccine. Originally intended to be a single-dose regimen, J&J's shot was seen as an attractive option to the two-dose regimen of Pfizer's and Moderna's for settings where recipients might not be available for a second shot. However, many scientists now view it as a two-shot vaccine.
Both J&J's and AstraZeneca's vaccines use viral vectors to deliver genetic material to cells, which then instructs them to make copies of the coronavirus' signature spike protein in order to stimulate an immune response.
While side effects to each are commonly mild, both have also been associated with the rare blockages, known as thrombotic thrombocytopenia and caused by blood clots that coincide with low platelet counts. The data "suggests a class effect" to the vaccine type, Doran Fink, deputy director of FDA's division of vaccines, told the Advisory Committee on Immunization Practices on Thursday.
Early findings suggested the main risk was concentrated in younger women. Fuller data have also shown cases in men and across all age groups, excepting men 65 and older, according to CDC data presented to ACIP.
Broadly, there have been about four cases of the blood clots for every 1 million doses administered, although the risk still is higher in younger women. The rate in women aged 30 to 39 is nearly 11 per million doses.
Use of the Pfizer and Moderna vaccines carries risks as well, most notably heart tissue inflammation in younger men. But there have been no deaths resulting from that side effect and 90% fully recover after three months, the CDC said. By contrast, through Dec. 9, there have been nine deaths following J&J's vaccine due to blood clot blockages.
In a presentation to ACIP, Penny Heaton, J&J's global research and development head for vaccines, stressed the shot's durability and its ease of use in settings — both in the U.S. and in low-income countries — where repeat vaccination isn't possible and the healthcare infrastructure is weaker. "We must save individuals here in the U.S. and facilitate equitable access both here and around the world," she said.
After hearing a presentation on the data and J&J's response, ACIP voted 15-0 to recommend that the Pfizer and Moderna vaccines be preferred over J&J's.
FDA's new warning, meanwhile, recommends against use of J&J's shot in patients with a history of post-vaccination blood clots, including after an initial dose of AstraZeneca's vaccine, which isn't authorized yet in the U.S.
J&J's vaccine has been little used in the U.S., with only 17 million doses administered to date, according to the CDC. Many of those individuals are choosing to receive a second dose of Pfizer or Moderna already, the data show.