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What are blood clotting reactions VIPIT and CSVT and do vaccines cause them?

This article was published on
April 21, 2021

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VIPIT and CSVT are acronyms for rare blood clotting reactions that have occurred in people who have received AstraZeneca or Johnson & Johnson's COVID-19 vaccines. It is uncertain whether or not the vaccines caused these clotting issues, but researchers are currently working to determine whether or not there is a link.

VIPIT and CSVT are acronyms for rare blood clotting reactions that have occurred in people who have received AstraZeneca or Johnson & Johnson's COVID-19 vaccines. It is uncertain whether or not the vaccines caused these clotting issues, but researchers are currently working to determine whether or not there is a link.

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What our experts say

VIPIT, or "vaccine-induced prothrombotic immune thrombocytopenia," is a very rare blood clotting condition that may be associated with COVID-19 vaccines. The condition is thought to occur between 5 and 28 days after some people receive the AstraZeneca vaccine. Most cases occurred in women under 60 years of age.

(It should be noted that some experts are referring to this as vaccine-induced thrombocytopenia and thrombosis (VITT) instead, but the two names both describe the same blood clotting phenomenon.)

Recent research from the European Medicines Agency (EMA) notes that VIPIT is likely to occur one time per every 100,000 shots. The EMA concluded that the benefits of COVID-19 vaccines outweigh the risks. People infected with COVID-19 are 100 times more likely to develop blood clotting than people who are not infected, according to scientists from the University of Oxford. Researchers from the school also noted that the risk of blood clotting after a COVID-19 infection was eight times higher than that of blood clotting after receiving the AstraZeneca COVID-19 vaccine. The virus appears to make blood in infected people more likely to clump up and form clots. While more research is being conducted around the potential links between AstraZeneca's vaccine and VIPIT, the degree of risk remains unclear and there are no obvious risk factors which might make a person more likely to suffer from VIPIT.

The EMA said the link between the vaccine and blood clots is "possible" and suggests including "unusual blood clots with low blood platelets" as very rare side effects of AstraZeneca's vaccine.

Symptoms that make you suspect VIPIT include: • persistent and severe headache • focal neurological symptoms • seizures, or blurred or double vision (suggesting CSVT or arterial stroke) • shortness of breath or chest pain (suggesting pulmonary embolism or acute coronary syndrome) • abdominal pain (suggesting portal vein thrombosis) or limb swelling, redness, pallor, or coldness (suggesting deep vein thrombosis or acute limb ischemia).

One of the types of blood clotting that occurred as part of VIPIT can cause symptoms similar to a stroke like weakness of limbs and facial muscles, headaches, seizures, and comas.

In April of 2021, Johnson &Johnson's COVID-19 vaccine was also linked with a rare clotting disorder after several people reported VIPIT symptoms. Like AstraZeneca's vaccine, these adenovirus vaccines caused nations to pause their vaccine use until more research could be conducted to determine the link between the shots and the clotting impacts.

One major challenge researchers are facing is how common blood clots are in the general population. This can make determining whether a vaccine causes this issue or if it would naturally occur within their body. For reference, it is estimated that one out of every four deaths worldwide is linked to blood clots.

Context and background

Recent news stories have linked blood clotting and related illnesses to certain vaccines, beginning with AstraZeneca's roll out in Europe in the first quarter of 2021. While research is ongoing to investigate the link between these events and the vaccines, there have been a number of documented cases of VIPIT and CSVT in people who received COVID-19 vaccines. Several European nations that are or were administering the AstraZeneca COVID-19 vaccine have noted the occurrence of blood clots in people who received the vaccine, some of them fatal, which caused them to pause or stop those vaccines from being administered. Similarly, people who received the Johnson & Johnson COVID-19 vaccine in the United States reported clotting issues so this country paused its use.

Resources

  1. Thrombosis and Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination List of authors (New England Journal of Medicine)
  2. Interim Guidelines: Diagnosis and Management of Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT) following AstraZeneca COVID-19 Vaccinations (United Nations)
  3. Guidance produced from the Expert Haematology Panel (EHP) focussed on Covid-19 Vaccine induced Thrombosis and Thrombocytopenia (VITT) (British Society for Haematology)
  4. Covid-19: Rare immune response may cause clots after AstraZeneca vaccine, say researchers (The British Medical Journal)
  5. Thrombotic Thrombocytopenia after Ad26.COV2.S Vaccination (New England Journal of Medicine)
  6. AstraZeneca’s COVID-19 vaccine: EMA to provide further context on risk of very rare blood clots with low blood platelets (European Medicines Agency)
  7. AstraZeneca’s COVID-19 vaccine: EMA finds possible link to very rare cases of unusual blood clots with low blood platelets (European Medicines Agency)
  8. Thrombocytopenia (low platelet count) (Mayo Clinic)
  9. COVID-19 (coronavirus): Long-term effects (Mayo Clinic)
  10. Why would a Covid vaccine cause rare blood clots? Researchers have found clues (STAT News)
  11. Blood clot risk higher for COVID than vaccines — Oxford (Deutsche Welle)
  12. Risk of rare blood clotting higher for COVID-19 than for vaccines (University of Oxford)
  13. Hard choices emerge as link between AstraZeneca vaccine and rare clotting disorder becomes clearer (Science)
  14. Concerns over rare clotting disorders halt use of Johnson & Johnson’s COVID-19 vaccine (Science)
  15. Cerebral venous thrombosis: a retrospective cohort study of 513,284 confirmed COVID-19 cases and a comparison with 489,871 people receiving a COVID-19 mRNA vaccine (University of Oxford)

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