What to Know About the Johnson & Johnson Vaccine Pause

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Federal officials recently called for an immediate “pause” in distribution of the Johnson & Johnson COVID-19 vaccine after six people — all women between the ages of 18 and 48 — developed a rare blood-clot disorder within two weeks of receiving the vaccine. One of the women died, and a second has been hospitalized in critical condition. As a result, and because doctors may need more information as to how to treat this extremely rare condition should it occur, federal officials have recommended the pause.

Here is what we know so far.

How will this affect the vaccination rollout?

Almost 7 million Americans have already been vaccinated with the Johnson & Johnson shot without experiencing significant side effects. Therefore, officials have emphasized that the blood-clot disorder is extremely rare and that the decision to pause distribution is being made out of an “abundance of caution.” Jeffrey D. Zients, the White House COVID-19 response coordinator, said the pause “will not have a significant impact” on the Biden administration’s vaccination timeline, which aims to inoculate every American who wants a vaccine by the end of May. The Pfizer and Moderna vaccines, neither of which has resulted in reports of any serious side effects, comprise the vast majority of the country’s vaccine supply — 23 million doses per week combined. Some officials worry the pause will slow progress at a time when risk of infection remains high, as does vaccine skepticism.

Others hope the takeaway will be more positive. “This should be reassuring, because it’s in our country’s interest to vaccinate as many people as possible, yet the FDA has acted promptly to pause until we know more,” says Vivek Cherian, an internal medicine physician at the University of Maryland health-care system. “This should inspire further confidence in the FDA and CDC, and not deter individuals scheduled for the other vaccines.”

What happens during the pause?

During the pause, scientists with the FDA and the CDC will investigate potential links between the vaccine and the rare blood-clot disorder in order to determine whether the FDA should continue authorizing its use among all adults. Because each of the patients experienced an onset of this extremely rare disorder, known as cerebral venous sinus thrombosis, within two weeks of vaccination, health officials are concerned the disorder may be an immune-system response triggered by the vaccine.

Peter Marks, the director of the Center for Biologics Evaluation and Research at the FDA, also told press that part of the reason for the pause is to inform doctors of best practices, as the standard treatment for blood clots (a blood thinner called heparin) can make this particularly rare blood-clot issue worse.

Isn’t this what happened with AstraZeneca?

Officials’ recommendation to pause the Johnson & Johnson vaccine is yet another public-relations crisis for the company, which earlier this month had to toss as many as 15 million doses after contamination with the AstraZeneca vaccine, which is not yet approved for use in the United States. The AstraZeneca vaccine has undergone a number of pauses of its own in response to similar concerns regarding rare blood-clotting issues. According to the New York Times, 222 people out of 34 million vaccinated in the U.K., E.U., and three other countries — most of them women under 60 — experienced “blood clots that were linked with a low level of platelets.” Most countries have since resumed distribution, having decided the benefits far outweigh the risks, while lamenting damage to citizens’ confidence in the vaccine as a result of the stoppages.

Both the Johnson & Johnson and AstraZeneca vaccines use an inactivated adenovirus to carry the genetic code for the SARS-2 spike protein (as opposed to the Pfizer and Moderna vaccines, which use mRNA), prompting concern from the Australian government, which recently said it won’t purchase the Johnson & Johnson vaccine. Still, health officials say there is no clear reason why an adenovirus-based vaccine should be any more likely to cause these rare blood-clot disorders.

What to Know About the Johnson & Johnson Vaccine Pause