2332. COVID-19 Primary Series and Booster Vaccination and Potential for Immune Imprinting

Abstract

Abstract Background Epidemiological evidence for immune imprinting was investigated in immune histories related to vaccination in Qatar from onset of the omicron wave, on December 19, 2021, through September 15, 2022. Methods Matched, retrospective, cohort studies were conducted to investigate differences in incidence of SARS-CoV-2 reinfection in the national cohort of persons who had a primary omicron infection, but different vaccination histories. History of primary-series (two-dose) vaccination was compared to that of no vaccination, history of booster (three-dose) vaccination was compared to that of two-dose vaccination, and history of booster vaccination was compared to that of no vaccination. Associations were estimated using Cox proportional-hazards regression models. Results The adjusted hazard ratio for incidence of reinfection, including also adjustment for differences in testing rate, in the two-dose cohort relative to that in the unvaccinated cohort was 0.43 (95% CI: 0.39-0.49). The adjusted hazard ratio comparing incidence of reinfection in the three-dose cohort to that in the two-dose cohort was 1.47 (95% CI: 1.23-1.76). The adjusted hazard ratio comparing incidence of reinfection in the three-dose cohort to that in the unvaccinated cohort was 0.57 (95% CI: 0.48-0.68). All adjusted hazard ratios appeared stable over 6 months of follow-up. Divergence in cumulative incidence curves in all comparisons increased markedly when incidence was dominated by BA.4/BA.5 and BA.2.75*. No reinfection in any cohort progressed to severe, critical, or fatal COVID-19. Conclusion History of primary-series vaccination enhanced immune protection against omicron reinfection, but history of booster vaccination compromised protection against omicron reinfection. These findings do not undermine the short-term public health utility of booster vaccination. Disclosures All Authors: No reported disclosures