US Health Officials Call For J&J Vaccine Pause Over 'Extremely Rare' Blood Clots

Citing an "abundance of caution," U.S. health authorities with the Centers for Disease Control and Prevention and the Food and Drug Administration are calling for a temporary pause in the distribution of Johnson & Johnson's COVID-19 vaccine over "extremely rare" cases of blood clots.

"As of 4/12, 6.8m+ doses of the J&J vaccine have been administered in the U.S. CDC & FDA are reviewing data involving 6 reported U.S. cases of a rare & severe type of blood clot in individuals after receiving the vaccine. Right now, these adverse events appear to be extremely rare," an FDA statement on Twitter read.

If the authorities' recommendations are carried out, Johnson & Johnson's vaccine would be the second to face such a halt.

In March, AstraZeneca's vaccine also came under scrutiny for blood clots in several European nations, with Germany, France, Spain, Ireland, the Netherlands, and Italy, among others, all suspending its use while health authorities investigated, CNBC reported.

Subsequent studies have linked the AstraZeneca vaccine to the blood clots in patients with abnormally low blood platelet counts. However, the European Medicines Agency determined that, given the rarity of the cases, the benefits of continuing use of the vaccine outweighed the risks.

Johnson & Johnson's vaccine is similar to AstraZeneca's.

Both are based on adenovirus viral vectors, which uses a genetically engineered common cold virus to deliver genetic instructions to the body to help it fight off infections without actually becoming infected.

However, where the AstraZeneca vaccine requires two doses to reach full efficacy, as the Moderna and Pfizer vaccines do, the Johnson & Johnson vaccine requires only a single dose, which gives it considerable promise in helping to end the pandemic.

However, many experts welcomed the CDC and FDA recommendation.

Dr. Carlos del Rio, executive associate dean of the Emory University School of Medicine at Grady Health System, told CNN that the health authorities' caution was warranted.

"I want to congratulate the CDC and the FDA for very quickly jumping on it, halting the vaccinations until we know more, and really trying to understand what's going on," Dr. del Rio said. "I think vaccine safety has always been a priority -- and I think this is exactly the right move until we understand what's going on and what's the way forward."

The CDC and FDA have a couple of different aims for the pause.

For one, the agencies would like time to properly investigate whether the blood clot cases are indeed related to the vaccine. For another, they'd like to prepare guidelines for healthcare providers and the public in dealing with the potential for blood clots.

"CDC will convene a meeting of the Advisory Committee on Immunization Practices (ACIP) on Wednesday to further review these cases and assess their potential significance. FDA will review that analysis as it also investigates these cases," the FDA wrote on Twitter.

"Until that process is complete, we are recommending this pause. This is important to ensure that the health care provider community is aware of the potential for these adverse events and can plan due to the unique treatment required with this type of blood clot."

It's worth underscoring, however, that blood clots are extraordinarily unlikely to occur.

"It's a very rare event," Dr. del Rio told CNN. "You're talking about 1 per million, and when you give millions of doses of vaccines, you will see events like this that you couldn't see in the clinical trial just because you didn't have millions of people enrolled."

In a statement, Johnson & Johnson noted that the company has also been working with European health authorities and has "made the decision to proactively delay the rollout of our vaccine in Europe."

The CDC and FDA also released recommendations to those who have received the Johnson & Johnson vaccine.

"People who have received the J&J vaccine who develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their health care provider," a press release read.

Due to the FDA and CDC recommendations, all federal health channels, including mass vaccination sites and community health centers, will temporarily cease administering the Johnson & Johnson vaccine, CNN reported.

Whether individual states pause the Johnson & Johnson vaccine as well will be up to their public health officials, however.

h/t: CNN