Association of COVID-19 Vaccination With Risk of Medically Attended Postacute Sequelae of COVID-19 During the Ancestral, Alpha, Delta, and Omicron Variant Eras.

Background: Uncertainty exists regarding the effectiveness of COVID-19 vaccine to prevent postacute sequelae of COVID-19 (PASC) following a breakthrough infection. While most studies based on symptom surveys found an association between preinfection vaccination status and PASC symptoms, studies of medically attended PASC are less common and have reported conflicting findings. Methods: In this retrospective cohort of patients with an initial SARS-CoV-2 infection who were continually empaneled for primary care in a large US health system, the electronic health record was queried for preinfection vaccination status, demographics, comorbidity index, and diagnosed conditions. Multivariable logistic regression was used to model the outcome of a medically attended PASC diagnosis within 6 months of SARS-CoV-2 infection. Likelihood ratio tests were used to assess the interaction between vaccination status and prevalent variant at the time of infection and between vaccination status and hospitalization for SARS-CoV-2 infection. Results: During the observation period, 6.9% of patients experienced medically attended and diagnosed PASC. A diagnosis of PASC was associated with older age, female sex, hospitalization for the initial infection, and an increased severity-weighted comorbidity index and was inversely associated with infection during the Omicron period. No difference in the development of diagnosed PASC was observed between unvaccinated patients and those vaccinated with either 2 doses of an mRNA vaccine or >2 doses. Conclusions: We found no association between vaccination status at the time of infection and development of medically diagnosed PASC. Vaccine remains an important measure to prevent SARS-CoV-2 infection and severity. Further research is needed to identify effective measures to prevent and treat PASC.