Increased risk of blood clots after COVID-19: higher with underlying conditions and more severe symptoms

Simon Collins, HIV i-Base

A study of more than one million people with confirmed COVID-19 in Swedish national registries between February 2020 and May 2021 reported increased risks of clotting and bleeding.

  • A 5-fold increased risk of deep vein thrombosis up to three months after covid-19 infection.
  • A 33-fold increased risk of pulmonary embolism (a blood clot in the lung) up to six months.
  • An almost double risk of bleeding events up to two months.

Cases were matched by age, sex, and county of residence to more than four million people who had not had SARS-CoV-2.

Deep vein thrombosis occurred in 401 vs 267 cases vs controls (absolute risk 0.04% vs 0.01%). Pulmonary embolism in 1,761 vs 171 (absolute risk 0.17% vs 0.004%. And first bleeding event in 1,002 vs 1,292  (absolute risk 0.10% vs 0.04%). Rates were higher in people with underlying conditions and who had more severe COVID symptoms.

The researchers said their results supported the benefits of thromboprophylaxis, especially for high risk patients, and showed the importance of vaccine protection.


Tang ME et al. People with HIV have a higher risk of COVID-19 diagnosis but similar outcomes to the general population. BMJ, doi: 10.1111/hiv.13312. (08 April 2022).

This report was first published on 1 April 2022.

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