BACK

Does flying increase the risk of blood clots in people who have been vaccinated?

This article was published on
June 11, 2021

This explainer is more than 90 days old. Some of the information might be out of date or no longer relevant. Browse our homepage for up to date content or request information about a specific topic from our team of scientists.

Flying does not increase the risk of blood clots in people who have been vaccinated. Though the risk of blood clots increases in people who are flying, this is not related to COVID-19 vaccines and these types of blood clots are different than the blood clots that have occurred in very few cases of people who have received the AstraZeneca or Johnson & Johnson vaccines.

Flying does not increase the risk of blood clots in people who have been vaccinated. Though the risk of blood clots increases in people who are flying, this is not related to COVID-19 vaccines and these types of blood clots are different than the blood clots that have occurred in very few cases of people who have received the AstraZeneca or Johnson & Johnson vaccines.

Publication

What our experts say

There is no evidence that air travel can increase the risk of blood clots in people who have received COVID-19 vaccines.

Though people can develop blood clots while flying, most likely deep vein thrombosis (DVT), these are unrelated to the vaccine. These clots most often occur in the leg during flights due to a lack of movement, staying seated for long periods of time, damage and slow blood flow between the veins, and air pressure, among other things. These clots in the leg may break off and travel to the lung, potentially resulting in what is called a pulmonary embolism.

Flying is a known risk factor in increasing the likelihood of blood clots. So is traveling by car, bus, or train. Most people who develop DVT as a result of flying have other factors that increase their risks such as a history of blood clots, recent surgeries, injuries, blood clots, hormone replacements, pregnancy, older age, obesity, and others.

Currently, no data has linked an increase in blood clots while flying with any COVID-19 vaccines. The clots that have occurred in a tiny part of the vaccinated population occur in unique and unusual areas; much different than DVT.

COVID-19 vaccines created by AstraZeneca and Johnson & Johnson have been associated with clots in veins, including in the brain, according to a recent study in the British Medical Journal. These types of clots are called cerebral venous sinus thrombosis (CSVT) and they are very rare.

In an analysis of people who had experienced clotting (also called 'thrombosis') after receiving vaccines, German scientists found that nine people who received the AstraZeneca vaccine experienced CSVT. Three others had blood clots in the abdominal veins, and three had pulmonary embolisms, which are blood clots in the lungs. One had bleeding in the brain, and four had other types of blood clots. Five patients experienced blood clots in different parts of the body that block small blood vessels.

Other studies have shown that a very small number of people who had received AstraZeneca's vaccine had experienced clots in the arteries that carry blood from the heart into other organs in the body.

The United States Centers for Disease Control and Prevention notes that the type of blood clots that occurred in people who received the Johnson & Johnson vaccines were also CSVT. The agency believes the benefits of the vaccine still outweigh the risks. These clots have been found almost entirely in young women under 50 years old. The risk of clotting after receiving this vaccine is roughly 9 in 10 million and much higher in the general population, as more than 1 in 1000 people experience clotting more generally.

Context and background

Social media posts have falsely linked the rare side effect of blood clots from specific COVID-19 vaccines to the heightened risk of blood clots while flying. One popular story that has been circulating claimed that airline executives recently met to discuss the risks of carrying vaccinated passengers because they may be more susceptible to blood clots while on board.

Several media outlets as well as numerous airline companies have vehemently denied this meeting occurred. The International Air Transport Association also released a statement debunking this claim. Further, there is no evidence tying extremely rare blood clotting linked to COVID-19 vaccines with blood clots occurring due to long-distance related travel.

Resources

  1. Thrombotic Thrombocytopenia after ChAdOx1 nCov-19 Vaccination (The New England Journal of Medicine)
  2. Thrombosis and Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination (The New England Journal of Medicine)
  3. Arterial events, venous thromboembolism, thrombocytopenia, and bleeding after vaccination with Oxford-AstraZeneca ChAdOx1-S in Denmark and Norway: population based cohort study (The BMJ)
  4. The Johnson & Johnson Vaccine and Blood Clots: What You Need to Know (Yale Medicine)
  5. EU drug regulator finds link between AstraZeneca vaccine and blood clots (Reuters)
  6. CDC Recommends Use of Johnson & Johnson’s Janssen COVID-19 Vaccine Resume (The United States Centers for Disease Control and Prevention)
  7. Covid vaccines and rare clots - what you need to know (BBC News)
  8. “Vaccine-Induced Covid-19 Mimicry” Syndrome: Splice reactions within the SARS-CoV-2 Spike open reading frame result in Spike protein variants that may cause thromboembolic events in patients immunized with vector-based vaccines (Research Square)
  9. Flying + Vaccine Blood Clots claim (Instagram)
  10. Blood Clots and Travel: What You Need to Know (The United States Centers for Disease Control and Prevention)
  11. Air travel and the risk of thromboembolism (Internal and Emergency Medicine)
  12. Flying, pregnancy, or taking the pill all carry much higher blood clot risks than the J&J vaccine (Quartz)
  13. Studies suggest link between blood clots, AstraZeneca COVID vaccine (Center for Infectious Disease Research and Policy)
  14. No record airlines met to discuss liabilities related to vaccine (The Associated Press)

Media briefing

Media Release

Expert Comments: 

No items found.

Q&A

No items found.