All known cases have occurred in Women aged 18-48 years. One of the women died and another is still in serious condition. However, CDC officials said it might be difficult to put gender limits in place instead of age restrictions. Several European countries have used this approach for a similar vaccine from AstraZeneca, which can also be linked to clotting problems.
The CDC panel, known as the Advisory Committee on Immunization Practices, not only reviews the six reported cases of blood clots in J&J recipients, but also discusses whether the risk of using the shot outweighs the benefit.
The J&J vaccine is convenient to administer as it only takes one dose and can be stored in the refrigerator. However, CDC officials noted that the country has adequate and safe vaccines from Pfizer and Moderna. These recordings use mRNA technology, while Johnson & Johnson and AstraZeneca vaccines are based on adenoviruses.
“The decision isn’t necessarily getting a Janssen vaccine versus the risk of Covid-19,” said CDC official Sara Oliver, referring to the J&J department doing the shot. “The decision could be to get one Janssen vaccine versus getting another mRNA vaccine.”
Pfizer and Moderna have each promised the US 300 million doses by the summer. Pfizer said Tuesday that it is ahead of production schedule and can deliver all of these shots by mid-July.
The US can easily use these two shots to vaccinate its adult population, according to Jeff Zients, White House Covid-19 Response Coordinator. However, J&J was expected to play a bigger role in the country’s vaccination schedules by late spring, especially as the US moves towards immunizing children and considers the potential need for booster vaccinations in the months or years ahead.
Aran Maree, head of Janssen’s Global Medical Organization, said the company found that four of the women who developed blood clots known as cerebral venous sinus thrombosis, or CVST, had low platelet counts. Three of the patients had other blockages, including the portal vein of the abdomen.
Maree said an additional coagulation case has been reported but specific details are pending. There were also two additional reported CVST cases in two different clinical trials, he said.
Neither the company nor regulators know if any of the known coagulation cases involved pregnant or postpartum individuals, but one person took oral contraceptives.
Maree said five of the reported cases – one in a clinical trial and four after vaccination – were treated with the blood-thinning heparin. While heparin is commonly used to treat typical blood clots, scientists say the drug can make the types of clots that are tested for links to the J&J vaccine worse.
The Food and Drug Administration authorized J&J single dose vaccine in case of emergency at the end of March. At the time, concerns about blood clots were noted in some subjects. However, not enough data were provided to establish a link to the vaccine. Although many of the people who developed blood clots in the study had health problems, a 25-year-old man with no preconditions had a severe case. The FDA advised providers to monitor for more blood clots in the general population in order to learn more about potential risks.