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Blood clots extremely rare after J&J vaccine

A blood clot

The Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA) on April 23, 2021, lifted the pause on the use of the Johnson & Johnson (J&J) COVID-19 vaccine.

After investigating reports of a rare type of blood clot, experts determined that the benefits of the vaccine still outweigh the risks.

Here's what you should know:

It's an extremely rare event

As of April 23, over 8 million people in the U.S. had been vaccinated with the J&J vaccine. Of those, 15 people reported developing severe blood clots. Nearly all were adult women under 50. For women between 18 and 49 years old, the chances of developing this problem are about 7 in 1 million. For women 50 and older and men of all ages, the chances are even smaller.

We don't know enough yet to say exactly how the vaccine creates this side effect. One theory suggests some patients may have an unusual immune response that causes low levels of blood platelets. But experts say there's enough evidence to suggest the vaccine does play a role.

CDC and FDA will continue to monitor the safety of all COVID-19 vaccines.

What you can do

As a precaution, it's a good idea to watch for these possible symptoms of a blood clot for three weeks after you receive the J&J vaccine:

  • Severe or persistent headaches or blurred vision.
  • Shortness of breath.
  • Chest pain.
  • Leg swelling.
  • Persistent abdominal pain.
  • Easy bruising or tiny blood spots under the skin beyond the injection site.

If you have any of these signs or symptoms, get medical help right away.

Which vaccine should you get?

As CDC and FDA continue to monitor these rare events, it's important to remember that COVID-19 vaccines are very safe overall and highly effective. They offer our best way out of the pandemic.

This type of blood clot has not been seen in any of the millions of people who have received the Moderna or Pfizer vaccines. If you have any questions or concerns about which vaccine is right for you, talk with your doctor, nurse or vaccine clinic.

Want to get more facts about COVID-19 vaccines? Check out our Coronavirus health topic center.

Reviewed 9/26/2021

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