Abstract
INTRODUCTION: With the advent of the Omicron variant, there are concerns about the efficacy of current vaccinations, especially among immunocompromised/immunosuppressed patients. Our aim was to determine the efficacy of the first booster dose against Omicron. METHODS: This was a retrospective cohort study using a well-established inflammatory bowel disease (IBD) cohort in the Veterans Health Administration. We followed patients on baseline IBD medications through the month of January 2022 during the Omicron COVID-19 wave and created adjusted models for vaccination and boosting effectiveness in reducing SARS-CoV-2 infection, hospitalization, and all-cause mortality. RESULTS: A total of 22,756 patients with IBD were included, of whom 34.9% had received a booster dose. During follow-up, 622 patients (2.7%) were diagnosed with SARS-CoV-2 infection. In adjusted models, booster status was associated with a 30% reduced hazard of SARS-CoV-2 infection (hazard ratio 0.70 vs unvaccinated status, 95% confidence interval 0.56-0.88, P = 0.002), translating to 25.05% effectiveness. Boosted status was also significantly associated with reduced COVID-19 hospitalization (hazard ratio 0.35, 95% confidence interval 0.16-0.74, P = 0.006), demonstrating a 65.06% effectiveness in adjusted models. There was no significant association between vaccination status and all-cause mortality in adjusted models. DISCUSSION: The boosted state was associated with a lower risk of SARS-CoV-2 infections and COVID-19-related hospitalization. Efficacy was lower than what has been seen against previous variants and decreased with prolonged duration from the booster. These findings suggest that patients with IBD, especially those who are immunosuppressed, should consider getting a second booster as per Centers for Disease Control and Prevention recommendations.