Thrombosis with thrombocytopenia syndrome happens when a person has both blood clots and low platelet counts after receiving certain COVID-19 vaccines.

Thrombosis with thrombocytopenia syndrome (TTS) is also known as vaccine-induced immune thrombotic thrombocytopenia (VITT). It’s a new, very rare but serious condition.

TTS happens when a person has both blood clots (thrombosis) and low platelet counts (thrombocytopenia) after receiving certain COVID-19 vaccines.

Keep reading to learn more about TTS — its symptoms, causes, diagnosis, treatment, and potential complications.

TTS and COVID-19 vaccines

COVID-19 vaccines are very safe for most people. TTS is an extremely rare occurrence, with only a small number of cases reported after receiving certain types of COVID-19 vaccines.

According to the Centers for Disease Control and Prevention (CDC), the Johnson and Johnson COVID-19 vaccine can cause TTS in some people. Still, the occurrence is very rare — TTS has been reported in approximately four cases out of 1 million doses of the Johnson and Johnson vaccine.

In response to the safety risks, on May 5, 2022, the Food and Drug Administration (FDA) issued a press release noting limited the use of the Johnson and Johnson vaccine. Now, this vaccine can only be given to people ages 18 years and older who:

  • cannot receive the mRNA-based Pfizer-BioNTech and Moderna COVID-19 vaccines — for example due to an allergic reaction
  • refuse to get the Pfizer and Moderna vaccines

There are other vaccines that can increase the risk of TTS, such as the AstraZeneca vaccine. But none of the other vaccines are used in the United States.

Symptoms of TTS may occur within a few days to a few weeks after receiving a COVID-19 vaccine. They typically include:

Medical emergency

These symptoms require immediate medical evaluation. Call emergency medical services or go to the nearest emergency room if you or your loved ones experience any of these symptoms after receiving a COVID-19 vaccine. Untreated TTS may result in death.

The mechanism that causes TTS after COVID-19 vaccination is not yet understood. We do know that it mainly affects people who received adenovirus-based vaccines. The risk of TTS is far lower in people receiving injectable mRNA vaccines.

TTS is similar to a condition called heparin-induced thrombocytopenia, which is an adverse reaction to a medication that prevents blood clots (anticoagulant).

Risk factors for TTS include:

Speak with a healthcare professional if you have any of these risk factors and are concerned about getting TTS after COVID-19 vaccination. They will help choose the best vaccine for you.

TTS is extremely rare. It has been reported in approximately four cases out of 1 million doses of the Johnson and Johnson COVID-19 vaccine. The risk is far lower for people who’ve received other vaccines used in the United States.

It’s important to remember that the risk of developing TTS is much lower than the risk of developing severe complications from COVID-19 itself.

Complications of TTS can arise from having blood clots and low platelet counts.

Blood clots can cause life threatening complications if they stop blood from reaching vital organs. Some of these complications include:

Having a low platelet count can additionally cause you to bleed easily and for a longer time than typically expected. It’s especially dangerous if you have internal bleeding in one of your vital organs.

Medical emergency

Call emergency medical services or go to the nearest emergency room if you experience the following symptoms within a week to a month of receiving a COVID-19 vaccine:

  • shortness of breath
  • chest pain
  • leg swelling
  • severe headache
  • bruising or bleeding
  • severe abdominal pain
  • vision changes
  • unusual rash

To diagnose TTS, a doctor will perform a physical exam and ask about your medical history. They will also likely order the following tests:

Doctors may also order other tests, such as imaging, if they suspect blood clots in one of your organs.

TTS is a very new condition. Healthcare professionals are still learning how to best approach its treatment. Because of the similarity between TTS and heparin-induced thrombocytopenia (HIT), they often use HIT treatment approaches to manage TTS. These approaches include using:

Your doctor may suggest other treatment strategies based on your specific case.

TTS is a rare but serious condition that can happen after receiving certain COVID-19 vaccines. Out of the vaccines used in the United States, the Johnson and Johnson vaccine has been associated with this condition, although the risk is still very low.

TTS is a medical emergency. Prompt treatment is required to avoid serious complications. It also important to note that TTS may lead to death.

TTS is a new condition. Scientists and healthcare professionals are still learning what causes it and how to best treat it. Be sure to talk with a healthcare professional if you have any concerns about your risk of developing TTS after COVID-19 vaccination.

It’s important to remember that the risks associated with COVID-19 vaccination are significantly lower than the risks of serious complications COVID-19 itself can cause.