People who got blood clots after a Johnson & Johnson vaccine got them within two weeks of their shot

Business Insider US
Registered Nurse Robert Orallo administers the Pfizer Covid-19 vaccine at the Blood Bank of Alaska in Anchorage on March 19, 2021.

Johnson & Johnson reported that six women, out of 6.8 million people dosed, developed cases of serious blood clots six to 13 days after vaccination. The blood clots occurred in women between 18 to 48 years old.

All women had a cerebral venous sinus thrombosis (CVST) blood clot, which is when there's a blood blockage in the brain channels. The blockage prevents the brain from draining blood and can lead to a hemorrhage. The women also had low levels of blood platelets.

In a briefing on Tuesday morning, the US Food and Drug Administration (FDA) said there is no evidence of a causal relationship between the vaccine and the blood clots.

Though the adverse event is extremely rare, the Centers for Diseases Control and Prevention (CDC) and FDA recommended a pause in vaccinating people with the J&J vaccine.

CVST blood clots have also been reported in a small number of people - mainly women under 60 - who got the AstraZeneca Covid-19 vaccine, which uses a similar vaccine technology to J&J.

How to spot symptoms of a blood clot

The CDC and FDA said patients should seek medical care if they have the following symptoms within three weeks of their J&J shot:

  • Severe headache
  • Abdominal pain
  • Leg pain
  • Shortness of breath

Other signs of a blood clot include:

  • Chest pain
  • Neurological symptoms, including severe and persistent headaches or blurred vision

In general, the World Health Organization recommends that if you have severe side effects four to 20 days after vaccination, you should go to the doctor.

Blood clots are typically treated with anti-clotting medicine. Nonetheless, the women who got blood clots after the J&J shot will receive other treatment, as anti-clotting drugs may be dangerous in their situation.

Severe complications from blood clots can be avoided if they're caught early.

The FDA and CDC are reviewing patient safety data before resuming J&J vaccinations.

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