Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) and COVID-19

COVID-19 vaccine
VITT is an extremely rare side effect of the COVID-19 vaccine

Vaccine-induced immune thrombotic thrombocytopenia (VITT), also called vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), is an extremely rare side effect of the COVID-19 vaccine. VITT is characterized by the presence of two conditions at the same time:

  1. Thrombosis: formation of blood clots, often in unusual sites like the brain 
  2. Thrombocytopenia: low platelets

VITT is similar to another condition called heparin-induced thrombocytopenia (HIT). But while HIT is caused by the medication heparin, VITT is associated with the Johnson & Johnson/Janssen or AstraZeneca COVID-19 vaccines. The condition has not been reported in people who have received the Pfizer or Moderna vaccines.

According to the Centers for Disease Control and Prevention (CDC), there have only been 6 cases among over 6 million people who received the Johnson & Johnson/Janssen COVID-19 vaccine. The AstraZeneca vaccine is not available in the U.S.

Researchers continue to investigate these cases to better understand what causes VITT and the overall benefits and risks involved in vaccine administration.

Who is at risk for VITT?

There are no specific risk factors for developing VITT. Most people who developed VITT were under the age of 60. And while all of the cases in the U.S. occurred in women who received the Johnson & Johnson vaccine, in other countries VITT occurred in both men and women who received the AstraZeneca vaccine.

There is no evidence that people with a history of thrombosis, thrombophilia or HIT are at higher risk for VITT. There is also no need to take medications or blood thinners like aspirin to prevent VITT since the occurrence of VITT is so rare.

A COVID-19 infection can lead to severe health risks, including lung impairment, blood clot formation and death. These risks far outweigh the very low risk of VITT.

What are symptoms of VITT?

VITT can occur 4-28 days after receiving the Johnson & Johnson/Janssen vaccine. Symptoms may include:

If you notice any of the above systems, report them to your doctor immediately. Your doctor may be able to evaluate your condition using computed tomography (CT) or magnetic resonance (MR) venograms, blood counts and other lab tests.

Are COVID-19 vaccines safe?

If you did receive the Johnson & Johnson vaccine, keep in mind that the window of risk is narrow (4-28 days after vaccination). So if you have passed that window without the symptoms described above, you can rest assured it’s almost certain you are not at risk for VITT.

Health researchers and scientists are keeping a close eye on COVID-19 vaccines. Overall, the COVID-19 vaccines available in the U.S. are very safe and effective at preventing you from getting infected by the virus. If you are eligible to receive a vaccine, you should get it to protect yourself against the disease. Side effects such as short-lived pain or fever are far outweighed by the benefits of being protected against the disease and its complications.

Cardiology Magazine. Vaccine-induced Thrombotic Thrombocytopenia (VITT) and COVID-19 Vaccines: What Cardiovascular Clinicians Need to Know. American College of Cardiology. April 21, 2021.

Centers for Disease Control and Prevention. CDC Recommends Use of Johnson & Johnson’s Janssen COVID-19 Vaccine Resume.