DALLAS, Thursday, April 15, 2021 – Earlier this week, the Centers for Disease Control and Prevention (CDC) and the U.S. Food & Drug Administration (FDA) recommended a pause in administration of the Johnson & Johnson (Janssen) COVID-19 vaccine because six women, ages 18-48 years, of the nearly 7 million adults who have received this vaccine experienced cerebral venous sinus thrombosis (CVST), or blood clots in the brain’s veins (not in the arteries, as is the case for most strokes).

CVST is an extremely rare but serious type of stroke caused by a blood clot in a part of the brain known as the venous sinus, involving veins that carry blood away from the brain. Spontaneous CVST is estimated to affect 5 of every 1 million people in the world annually. It can cause serious disability or even death. In contrast, the vast majority of strokes (approximately 87% of nearly 800,000 strokes in the U.S. annually) are ischemic strokes – blood clots in the arteries that lead to interruption of nourishing blood flow to the brain.  

When should you worry that you may have CVST, or blood clotting elsewhere in the body, as compared to some of the typical symptoms after the COVID-19 vaccine, or compared to symptoms of an ischemic stroke?

CVST and Other Blood Clot Symptoms (CVST occurs in the veins of the brain; if associated with vaccine, cases occurred several days to 2 weeks after being vaccinated; blood clots may also occur in other blood vessels, like those in the legs, lungs or abdomen)

  • Severe headache
  • Blurry vision or shortness of breath
  • Fainting or loss of consciousness
  • Weakness
  • Sensory Changes
  • Confusion or trouble speaking
  • Seizures
  • Abdominal pain
  • Leg pain
  • Difficulty breathing/shortness of breath

Symptoms occur several days and up to 2 weeks after receiving the Johnson & Johnson (Janssen) COVID-19 vaccine. Call 911 to receive emergency medical care as soon as possible. 

Typical COVID-19 Vaccine Symptoms (usually within 24-48 hours of receiving the vaccine)

  • Tiredness
  • Headache
  • Muscle pain
  • Chills
  • Fever
  • Nausea

Symptoms usually pass within 36-48 hours after receiving the vaccine. If symptoms are severe and include difficulty breathing, seek immediate medical attention – call 911 or go to the  nearest emergency room.

Ischemic Stroke Symptoms (occurs in the arteries that provide nourishing blood flow to the brain)

  • Remember FAST:
    • F=Face drooping
    • A=Arm weakness
    • S=Speech difficulty or slurred speech
    • T=Time to call 911.

If someone shows any of these symptoms, even if the symptoms go away, call 911 to receive emergency medical care as soon as possible. Check the time so you can tell emergency responders when the first symptoms appeared.

  • Other symptoms may include sudden headache, vision changes, or sudden loss of balance.
  • Not related to vaccine.
  • About 1-2% of patients hospitalized with COVID-19 may experience ischemic strokes.

The following statement reflects the views of the American Heart Association/American Stroke Association and its science leaders:

  • President Mitchell S.V. Elkind, M.D., M.S., FAHA, FAAN,
  • Immediate Past President Robert A. Harrington, M.D., FAHA,
  • President-Elect Donald M. Lloyd-Jones, M.D., Sc.M., FAHA,
  • Chief Science and Medical Officer Mariell Jessup, M.D., FAHA, and
  • Chief Medical Officer for Prevention Eduardo Sanchez, M.D, M.P.H., FAAFP.

“These recently reported CVST blood clots are very rare adverse events (less than one in one million), and the recommended pause in administration of the Johnson & Johnson (Janssen) vaccine confirms that ongoing monitoring and transparency in the vaccine process are working. The constant review promised by the CDC and FDA, as well as the commitment throughout the scientific and medical field to ensure the safety of the vaccines, remain firm. These events are so uncommon that they only appeared after clinical trials concluded, when millions  of people had been vaccinated, unlike the thousands in the original vaccine trials. We await the findings and updated guidance from the CDC and FDA urgent review of CVST associated with the Johnson & Johnson (Janssen) COVID-19 vaccine, expected next week.

We continue to urge everyone to receive a COVID vaccine as soon as they can receive it. We concur with the CDC’s and FDA’s recommendations for people who have received the Johnson & Johnson (Janssen) vaccine – if they develop severe headache, abdominal pain, leg pain or shortness of breath within 3 weeks of receiving the vaccine, they should quickly contact their health care professional.

The American Heart Association – which has been carefully tracking COVID-19 and its disproportionately negative effects on older adults; people with underlying medical conditions; and Black, LatinX and American Indian/Alaska Native people – strongly encourages everyone to get vaccinated with an approved COVID-19 vaccine.

In particular, people with cardiovascular risk factors such as high blood pressure, obesity, and type 2 diabetes, those with heart disease, and heart attack and stroke survivors should get vaccinated as soon as possible because they are at much greater risk of a negative outcome from the virus than they are from the vaccine. We are confident the benefits of vaccination far exceed the very small, rare risks. The risks of vaccination are also far smaller than the risks of COVID-19 and its potentially fatal consequences.

We recommend people who have medical conditions, especially those with propensity for blood clotting, consult with a health care professional before seeking vaccination to discuss potential increased risks. In addition, the Association reiterates the importance of handwashing, social distancing and wearing masks as vaccinations continue, particularly for people at high risk of infection and/or severe COVID-19. These simple precautions remain crucial to protecting people from the virus that causes COVID-19. They also are crucial to getting us all back to normal activities.

Individuals should refer to their local and state health departments for specific information about when and where they can get vaccinated. We urge everyone to get vaccinated.”

The American Heart Association remains deeply concerned about the COVID-19 pandemic. The Association’s priority is the health and well-being of all individuals and their families today and in the future, in every community, everywhere.

Additional Resources:

The Association receives funding primarily from individuals. Foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers are available here, and the Association’s overall financial information is available here.

About the American Heart Association

The American Heart Association is a relentless force for a world of longer, healthier lives. We are dedicated to ensuring equitable health in all communities. Through collaboration with numerous organizations, and powered by millions of volunteers, we fund innovative research, advocate for the public's health and share lifesaving resources. The Dallas-based organization has been a leading source of health information for nearly a century. Connect with us on heart.orgFacebookTwitter or by calling 1-800-AHA-USA1.  


For Media Inquiries: 214-706-1173,  AHAcommunications@heart.org

Michelle Kirkwood: 703-457-7838, michelle.kirkwood@heart.org

Alexson Calahan: 515-994-0772, alexson.calahan@heart.org

Public Inquiries: 1-800-AHA-USA1 (242-8721)

heart.org and stroke.org