Estimating the Effect of Coronavirus Disease 2019 (COVID-19) Vaccination and Infection Variant on Post-COVID-19 Venous Thrombosis or Embolism Risk.

Background: Previous research has shown that vaccination reduces risk of post-coronavirus disease 2019 (COVID-19) venous thrombosis or embolism (VTE), but the effect of vaccine boosting on post-COVID-19 VTE risk reduction is unclear. We sought to estimate the effect of COVID-19 vaccination on the risk of post-COVID-19 VTE and to examine if the magnitude of this association differed among variant eras.
Methods: We performed a case-control study of Military Health System (MHS) beneficiaries who tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2020-2022. Cases were defined as those with medically attended VTE within 90 days after their first positive SARS-CoV-2 test; controls were defined as SARS-CoV-2 infections without incident VTE by 90 days. Multivariate logistic regression estimated the odds of post-SARS-CoV-2 VTE based on pre-COVID-19 vaccine status, adjusting for other VTE risk factors.
Results: A total of 4646 MHS beneficiaries were included in this analysis; 1370 received a primary vaccine series and a further 790 received at least 1 booster at time of infection; 71 had VTE within 90 days of SARS-CoV-2 infection. Those who were vaccinated had lower odds of VTE (adjusted odds ratio [95% confidence interval]) compared to the unvaccinated following infection (primary series: 0.28 [.13-.62]; booster dose: 0.06 [.01-.46]). Post-COVID-19 VTE risk was lowest during the Omicron era, but VTEs were too rare to examine for an interaction of variant era and vaccine effect.
Conclusions: Among MHS beneficiaries, COVID-19 vaccination was associated with a reduced risk of post-COVID-19 VTE diagnosis; estimated risk reduction was larger among those who received a booster.
Competing Interests: Potential conflicts of interest. S. D. P., T. H. B., D. R. T., and M. P. S. report that the Uniformed Services University (USU) IDCRP, a US DOD institution, and HJF were funded under a Cooperative Research and Development Agreement to conduct an unrelated phase 3 COVID-19 monoclonal antibody immunoprophylaxis trial sponsored by AstraZeneca. The HJF, in support of the USU IDCRP, was funded by the DOD Joint Program Executive Office for Chemical, Biological, Radiological, and Nuclear Defense to augment the conduct of an unrelated phase 3 vaccine trial sponsored by AstraZeneca. Both trials were part of the US government COVID-19 response. Neither is related to the work presented here. R. C. M. receives research support paid to his institution from Sound Pharmaceuticals for an investigational COVID-19 therapeutic and from GeoVax for an investigational COVID-19 vaccine candidate, both unrelated to the work presented here. All other authors report no potential conflicts of interest.
(Published by Oxford University Press on behalf of Infectious Diseases Society of America 2024.)