Patients with hemophilia who contracted COVID-19 were not shielded from the risk of severe disease, according to a study published in the Journal of Thrombosis and Haemostasis. 

The COVID-19 pandemic disproportionately affected individuals with chronic illnesses. Studies have identified an acquired hypercoagulable state as culpable in driving disease severity in some patients. This means that all morbidities that can lead to a hypercoagulable state, such as cardiovascular, renal, or liver disease, can significantly raise the risk of severe COVID-19 infection. 

Hemophilia is a disease in which blood clotting is disrupted and slowed down significantly, leading some researchers to question whether patients with hemophilia have some immunity to severe disease. Thus, Sharathkumar and colleagues conducted their study to assess how hemophilia affects the COVID-19 disease course. 

Continue Reading

They performed a retrospective observational cohort study with patients with hemophilia A or B (n=300) who also contracted COVID-19. Patients were identified via the M3D Data enclave, which contains data from more than 75 healthcare facilities across the US. The research team also recruited controls who were matched in terms of propensity scores, which included variables such as chronic comorbidities, substance abuse, and smoking. 

Read more about hemophilia etiology 

In the study, the research team defined the “index counter” as the longest encounter associated with a COVID-19 diagnosis. In other words, if a patient had multiple clinical visits/hospitalizations, the longest time period of any visit was selected as the index counter. Outcomes were then observed from the start of the index encounter until 30 days after the end of said encounter. Primary outcomes were the occurrence of severe COVID-19 disease. 

The results of the study demonstrated that hemophilia conferred no benefits in terms of COVID-19 severity or mortality. This was also true for the risk of venous thromboembolism. However, the research team found that common risk factors for adverse outcomes, such as cardiovascular/liver disease, cancer, and dementia, are likewise associated with poorer outcomes in individuals with hemophilia. 

“Markers of severity, including ICU admission and need for oxygen therapy, were not different in patients with hemophilia compared to controls,” the authors concluded.  


Sharathkumar A, Wendt L, Ortman C, National COVID Cohort Collaborative Consortium, et al. COVID-19 outcomes in persons with hemophilia: results from a US-based national COVID-19 surveillance registryJ Thromb Haemost. Published online May 12, 2023. doi:10.1016/j.jtha.2023.04.040