Researchers found no increased risk for acute deep vein thrombosis (DVT) post-vaccination for any of the approved COVID-19 vaccines in the United States, according to data presented at the 2021 American Society of Hematology Annual Meeting. Investigators, led by Damon E. Houghton, MD, MS, of Mayo Clinic in Rochester, Minnesota, also found no significant difference in the risk for DVT post-vaccination between available vaccines. Taken together, these results should provide additional reassurance of the safety of approved COVID-19 vaccines, the authors noted.
This study analyzed the electronic medical records of 382,527 patients aged 18 or older with at least one COVID-19 vaccination from across the Mayo Clinic enterprise. Data on upper and lower DVT venous Duplex ultrasound reports occurring 90 days before or after vaccination were extracted and analyzed with a validated algorithm for DVT.
Pfizer was the most common vaccine administered (64.2%), followed by Moderna (31.6%) and Johnson & Johnson (4.3%). Women were most likely to receive Pfizer compared with Moderna and Johnson & Johnson (56.3% vs. 54.1% vs. 49.5%). Non-white patients were most likely to receive the Johnson & Johnson vaccine (21%), compared with Moderna (7.7%) or Pfizer (8.2%).
In total, 7,265 upper and lower venous Duplex ultrasounds were performed in 5,960 patients. More patients underwent ultrasound in the 90 days after vaccination compared with the 90 days prior to vaccination.
Acute DVT was found in 11.1% of ultrasounds (714 patients). The rate of acute DVT was 1.86 per 1,000 patients, which Dr. Houghton noted was similar to expected background epidemiologic rates.
There was no significant difference in the rate of DVT pre- to post-vaccination. Overall acute DVT post-vaccination occurred on 10.8% of ultrasounds compared with 11.6% pre-vaccination.
The researchers also compared rates of DVT between the available vaccines. In Johnson & Johnson-vaccinated patients, 7.0% were positive for acute DVT post-vaccination compared with 18.0% pre-vaccination (P=0.003). In Moderna-vaccinated patients, 11.0% were positive for acute DVT post-vaccination compared with 12.7% pre-vaccination. In Pfizer-vaccinated patients, 11.0% were positive for acute DVT post-vaccination compared with 12.7% pre-vaccination.
The hazard ratio (HR) for pre- versus post-vaccination was 0.68 for the Johnson & Johnson vaccine, 1.08 for the Moderna vaccine, and 1.20 for the Pfizer vaccine. After adjusting for age and sex, Pfizer and Johnson & Johnson COVID-19 vaccines did not have different risks for DVT compared with Moderna in the 90 days after vaccination (HR = 0.80; 95% CI 0.98-1.25 for Pfizer and HR = 0.75; 95% CI 0.42-1.32 for Johnson & Johnson).