SARS-CoV-2 breakthrough infection after artificial and hybrid immunization in healthcare workers

Abstract

Introduction. Current reports suggest that people with a history of SARS -CoV-2 infection and a complete vaccination status have greater protection against the symptomatic presentation of SARS -CoV-2. Objective. To compare the risk of becoming ill with COVID-19 between health personnel with a complete SARS -CoV-2 BNT162b2 vaccine status and a history of SARS -CoV-2 infection. Methodology. Historical cohort study in 1874 health workers of the Civil Hospital of Guadalajara immunized with the BNT162b2 vaccine between January and March 2021. After six months of follow-up, the non-exposed group (without a history of infection) was 1397 and the group exposed (with a history of infection) of 477
subjects. Results. The incidence of SARS -CoV-2 infection in the cohort was 39 cases, the risk of infection after immunization was 0,021, the lowest risk was identified in the hybrid immunization group (0,015 and 0,243), with a relative risk of 0,43 (95 % CI 0,17 to 1,09). Hybrid immunization contributed to a population-attributable risk reduction of 0,003 (R0 0,024; Rp 0,020). Hospitalization occurred in 7,69 % of confirmed cases with SARS -CoV-2. The risk of hospitalization in hybrid immunization is 0,210 and 0,143 in the artificial immunization group (RR 1,4 95 % CI 0,13 -16,11). Outcome. Hybrid immunization could
contribute to reducing the risk of infection for future variants of SARS -CoV-2 by enhancing the immunity generated by the vaccine against COVID-19.