One Center's Experience of Pulmonary Embolism after COVID-19: Impact of Vaccination Status

Background: The incidence of pulmonary embolism (PE) has increased since the outbreak of the COVID-19 pandemic and may be due to the observed hypercoagulable state. There is conflicting evidence that thromboembolism risk increases after vaccination and that vaccines decrease the probability of having a thromboembolic event. This study aimed to explore how vaccination status impacts occurrence of PE after a positive COVID-19 test. The hypothesis was that vaccinated, immunocompetent patients have a lower incidence of PE after COVID-19 compared to unvaccinated patients. Methods: This was a retrospective chart review at a teaching hospital in New England from 1/01/2021 to 3/31/2023 to identify the impact of vaccination status on the incidence of PEs after a positive COVID-19 test in immunocompetent patients. IRB exclusion was obtained. Subjects aged 12 to 80 years old who had PEs within 6 months of testing positive for COVID-19 were included; excluded were outside the age range, without documentation of PE and COVID-19 within 6 months, had orthopedic surgery within three months, chest trauma, thrombophilias, or immunodeficiency; received vector vaccine; and had multiple visits for a PE. Subjects were separated into vaccinated and unvaccinated groups. Charts were reviewed for age, sex, race, documented PE and positive COVID-19 test within 6 months, brand and number of vaccines, and exclusion criteria. Statistics used t-test with p-value 0.05. Results: Fifty subjects were coded for PE and COVID-19; 23 were excluded, leaving 27 subjects. Ages ranged from 12 to 80 years, with a mean of 63.8. Nineteen were male, 8 female; 23 white and 4 non-white. There were 12 unvaccinated, 15 vaccinated; T-value 1.37, p=0.183. There was no significant difference between development of a PE within six months of a positive COVID-19 test result regardless of vaccination status, which failed to reject the null hypothesis. These results were limited by small sample size. Discussion: This study found no correlation between vaccination status and PE within 6 months of COVID-19, which neither confirmed nor negated prior studies regarding the relationship between vaccines, PEs, and COVID-19. Further studies may serve to clarify the relationship.