Blood clots: Signs, symptoms and vaccines

Though very rare, it’s the risk for blood clots that paused the Johnson & Johnson COVID-19 vaccine.

A blood clot can form anywhere in the body and, most often, the body naturally dissolves them without showing any sign or symptom.

In the news lately, though, blood clots can also result in potentially devastating health conditions, such as a stroke, heart attack or pulmonary embolism.

A clot is formed when liquid blood within the body thickens and coagulates into a clump-like, semi-solid state. If they don’t naturally dissolve, clots can travel through the body’s blood vessels, increasing the likelihood of that clot obstructing blood flow, also called an embolism.

Risk factors can help physicians determine who among their patients are more likely to develop blood clots, and medications can help lower that risk.

Signs and risk factors

If the clot is in the arms or legs, symptoms can include:

• Swelling
• Pain
• Tenderness
• Red skin
• Warm sensation

A pulmonary embolism — a clot that travels to the lungs — can cause shortness of breath, cough and chest pain.

A potential stroke-causing blood clot within the brain causes symptoms of a sudden, severe headache and trouble seeing or speaking.

Risk factors:

• Older adults
• Family history
• Obesity
• Recent hospitalization, surgery or cancer treatment
• Injury
• Estrogen medication

Johnson & Johnson vaccine pause

At the time of the April 13 pause, six recipients of the more than 6.8 million administered shots developed a rare form of blood clot known as a cerebral venous sinus thrombosis, or CVST.

These rare clots form in the brain’s venous sinuses, preventing blood from draining out of the brain, which can cause the blood to leak into the brain’s soft tissue, possibly leading to a hemorrhage and symptoms of headaches, vision change, nausea, vomiting or seizure.

The six cases have all been reported in women aged 18 to 48.

The pause, officials say, is evidence that the program prioritizes vaccine safety as well as effectiveness. It has also allowed researchers to thoroughly investigate each case and, perhaps, make recommendations as to who should receive the Johnson & Johnson vaccine and who should receive one of the other approved vaccines.

This is not unprecedented. Other medications are currently on the market that carry the risk of blood clots forming.

It’s always advisable to discuss the risks of medications, including vaccines, with a physician.