Risk for Venous Thromboembolism Is Reduced by COVID-19 Vaccination

COVID-19 vaccination decreases the risk for post-infection venous thromboembolism (VTE), according to study results published in Open Forum Infectious Diseases.

Researchers conducted a case-control analysis of the Epidemiology, Immunology, and Clinical Characteristics of Emerging Infectious Diseases with Pandemic Potential (EPICC) study, a prospective cohort study that enrolled hospitalized and outpatient Military Health Systems (MHS) beneficiaries who tested positive for SARS-CoV-2 via reverse transcriptase-polymerase chain reaction (RT-PCR) between March 2020 and May 2022. The aim of this analysis was to assess the effect of COVID-19 vaccination on the risk for post-COVID-19 VTE, which was defined as venous thrombosis or embolism. Case individuals were defined as those with medically attended VTE within 90 days of their first SARS-CoV-2-positive test, while patients in the control group were defined as those with SARS-CoV-2 infections without incident VTE by day 90. To estimate the odds of post-SARS-CoV-2 VTE risk based on vaccination status, multivariable logistic regression was used.  

A total of 4646 participants (median age, 36 years; women, 36.7%; White, 54.8%) were included in this study. Overall, 71 (1.53%) cases of VTE were identified within 90 days of SARS-CoV-2 test positivity.

Patients in the case vs control group were older (53.1 vs 35.7; P <.01), presented with more comorbidities at the time of SARS-CoV-2 infection (median Charlson comorbidity index, 1 vs 0; P <.01), and were more likely to have a history of VTE (16.9% vs 0.9%).

The primary series vaccine was received by 9.9% and 29.8% of patients in the case and control groups, respectively (P <.01). Compared with 1.4% of case individuals who were boosted, 17.2% of patients in the control group were boosted (P <.01).

After controlling for age, sex, history of VTE, and Charlson comorbidity index, individuals who were vaccinated with the primary series only vs those who were unvaccinated at the time of infection had lower odds of post-COVID-19 VTE by day 90 (adjusted odds ratio [aOR], 0.28; 95% CI, 0.13-0.62). Similarly, participants who were boosted vs those who were unvaccinated at the time of infection also had lower odds of post-COVID-19 VTE by day 90 (aOR, 0.06; 95% CI, 0.01-0.46).

History of VTE was the covariate most strongly associated with risk for post-COVID-19 VTE (aOR, 8.83; 95% CI, 4.57-17.07). The likelihood of post-COVID-19 VTE also increased by 4% with each additional year of age (aOR, 1.04; 95% CI, 1.02-1.06).

Study limitations include the small number of patients with post-COVID-19 VTE in the cohort, use of patient-reported data, and reduced generalizability of results to other settings.

“Future study directions include examining the impact of boosting on post-COVID-19 VTE risk using a larger sample size (eg, MHS claims based datasets), especially in outpatient populations, and with future variants,” the researchers concluded.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on Infectious Disease Advisor