Johnson & Johnson vaccine pause: What the rare blood clotting issue means

The link to the vaccine isn’t definite, and cases are rare, but caution is necessary to ensure patient safety.

gloved hand fills a vaccine syringe [View Image] VCU and VCU Health have instituted a pause in the administration of the Johnson & Johnson vaccine. "We’re just being as safe as possible and don’t want to keep using the J&J vaccine until we have all of the facts," said Jeffrey Donowitz, M.D. (Getty Images)

On April 13, the Centers for Disease Control and Prevention and the Food and Drug Administration issued a statement recommending a pause in administering the Johnson & Johnson vaccine to combat COVID-19. The recommendation was made following six reported U.S. cases of a rare and severe type of blood clot in individuals who had received the vaccine. The individuals also had an unusually low platelet count.

In keeping with the CDC and FDA recommendation, VCU and VCU Health System are no longer using the J&J vaccine. Jeffrey Donowitz, M.D., a VCU Health expert in infectious diseases, discussed what the pause means in an interview with VCU Health News.

How common are the blood clots? Should I be worried?

So far only six cases have been discovered out of 6.8 million doses of the J&J vaccine administered in the United States. That’s about one in a million. So that’s extremely rare. Instituting a pause doesn’t mean the vaccine was necessarily responsible for the clots. We’re just being as safe as possible and don’t want to keep using the J&J vaccine until we have all of the facts.

Are some people more susceptible to the blood clots?

With only six known cases, we don’t have a great enough sample size to know if something is predisposing certain people to the blood clots. That’s what the FDA and the CDC will be studying.

Anywhere from 2 million to 14 million people develop blood clots each year in this country. It could be that the individuals who developed the blood clots would have developed them regardless of whether they received the vaccine or not. We just don’t know yet.  

If I’ve already gotten the J&J vaccine, is there anything I should look out for?

In the three to four weeks after getting the shot, if you develop a severe headache, leg pain, abdominal pain, easy bruising or shortness of breath, go to the emergency room and be very clear that you got the J&J vaccine. Remember, though, that the vaccine has not been proven to cause blood clots, and the number of cases has been extremely rare — one in a million.

Is VCU Health continuing to offer vaccinations? Will my upcoming vaccination be cancelled or postponed?

We’re using our Moderna and Pfizer vaccine supply for vaccination appointments. If you already have an appointment, your vaccination will likely take place. You will be contacted if we need to postpone your appointment.

How do we know the other vaccines are safe?

After a phase 3 trial concludes and the vaccine is released, we never stop studying it. There’s a vaccine adverse event reporting system we use. Anyone can enter a report of a possible reaction to a vaccine into the system. The system catches patterns that may indicate a potential problem.

We haven’t seen any patterns of adverse reactions with the Moderna and Pfizer vaccines, other than the relatively mild side effects we knew about from the phase 3 trials. In the U.S., over 100 million people have been vaccinated, and we’re not seeing this clotting issue with all three vaccines — and we’re using the same reporting system.

It gives me great comfort knowing that the safety net in place designed to catch the one-in-a-million side effect that may be missed in a phase 3 trial with 30,000 to 40,000 patients is working.

When will we know if the J&J vaccine is safe?

The CDC will convene a meeting of the Advisory Committee on Immunization Practices April 14 to further review these cases and assess their potential significance. The FDA will review that analysis as it also investigates these cases.

For more COVID-19 vaccine news, visit VCU Health’s COVID-19 vaccine page.

Subscribe to VCU News

Subscribe to VCU News at and receive a selection of stories, videos, photos, news clips and event listings in your inbox.