Venous thromboembolism risk following surgery during the COVID ‐19 pandemic

Summary Introduction SARS‐CoV‐2 infection is associated with an increased risk of venous thromboembolism. Data are lacking on how this risk altered during the COVID‐19 pandemic and following vaccination. We aimed to evaluate the 90‐day risk of postoperative venous thromboembolism during the pandemic. Methods We performed a retrospective cohort study of patients having abdominal, obstetric, orthopaedic, cardiac, thoracic or vascular surgical procedures using the OpenSAFELY‐TPP platform. Crude 90‐day risks of venous thromboembolism were calculated and crude and adjusted hazard ratios were derived from individual Cox proportional hazards models. Results In total, 1,800,540 procedures were performed with 15,390 individual venous thromboembolic events recorded within 90 days. The highest crude absolute risk was in the Alpha wave at 1.2%. Postoperative SARS‐CoV‐2 infection was associated with a 4.4‐fold increase in relative risk of 90‐day venous thromboembolism (adjusted hazard ratio 4.42, 95%CI 4.21–4.64) compared with those without. Recent SARS‐CoV‐2 infection was associated with an increased risk of venous thromboembolism (adjusted hazard ratio 4.03, 95%CI 3.78–4.30) compared with those without. Patients who were unvaccinated had the highest relative risk for 90‐day venous thromboembolism. A single dose of vaccine was associated with a 20% relative risk reduction of venous thromboembolism (adjusted hazard ratio 0.80, 95%CI 0.76–0.84). Discussion SARS‐CoV‐2 infection status and vaccination history were associated with 90‐day venous thromboembolism risk, with both recent and postoperative SARS‐CoV‐2 infection associated with an increased risk, whilst one dose of vaccine reduced the risk.