Study adds insight on 'rare but devastating' blood clots after AstraZeneca shot

A new study gives more details about cases of blood clots in people given AstraZeneca's COVID-19 vaccine, which researchers said are "rare but devastating," CNBC reported. 

The study, published Aug. 11 in The New England Journal of Medicine, was conducted by scientists from the Massachusetts Medical Society in Waltham. 

Eight things to know: 

1. The researchers analyzed the first 220 cases of the rare blood-clotting condition, known as vaccine-induced immune thrombocytopenia and thrombosis, reported in the U.K. The condition is characterized by a combination of blood clots and low platelet levels, and all cases in the study were reported between March 22 and June 6.
   
   
2. AstraZeneca's COVID-19 vaccine, though not approved for use in the U.S., is one of the most widely used COVID-19 shots in the world.
   
   
3. All people included in the study were given the first dose of the shot and went to the hospital with symptoms between five and 48 days after vaccination, with the average time being 14 days, CNBC reported.
   
   
4. The overall mortality rate for the patients included in the study was 22 percent.
   
   
5. Forty-one percent of patients who developed VITT had no diagnosed underlying health issues.
   
   
6. Eighty-five percent of the patients were younger than 60, with the average age being 48, CNBC reported. The U.K. began offering people under the age of 40 an alternative COVID-19 vaccine in May.
   
   
7. More than 23 million people in the U.K. have gotten two doses of AstraZeneca's vaccine as of July 28. Through that date, 411 suspected cases of VITT had been reported.
   
   
8. AstraZeneca published a study at the end of July which found the rate of VITT after the first dose of its vaccine was 8.1 per million and 2.3 per million after a second dose.
   
   "Recent real-world evidence drawn from millions of individuals shows that AstraZeneca's vaccine has a comparable safety profile with other vaccines and that incidences of thrombosis with thrombocytopenia are extremely rare and treatable," an AstraZeneca spokesperson told CNBC, adding that there's a much greater risk of getting a blood clot from COVID-19 than from a vaccine. 

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