Population-Level Relative Effectiveness of the COVID-19 Vaccines and the Contribution of Naturally Acquired Immunity. (7th December 2022)

• Record Type: Journal Article
• Authors: Shioda, Kayoko; Chen, Yangping; Collins, Matthew H; Lopman, Benjamin A
• Is Part Of: Journal of infectious diseases. Volume 227:Number 6(2023)
• Page Start: 773
• Page End: 779
• Publication Date: 2022-12-07
• Subjects: COVID-19 -- SARS-CoV-2 -- booster -- cumulative incidence -- naturally acquired immunity -- proportion of the population ever infected -- seroprevalence -- vaccine coverage -- vaccine-induced immunity -- waning antibodies; Communicable diseases -- Periodicals; Diseases -- Causes and theories of causation -- Periodicals; Medicine -- Periodicals; Communicable Diseases -- Periodicals; Electronic journals; 616.9
• DOI: 10.1093/infdis/jiac483
• Languages: English
• ISSNs: 0022-1899

Abstract

Abstract : Vaccination with the primary series was strongly associated with reduction in COVID-19 mortality at state level in the Alpha, Delta, and Omicron wave. This effect did not vary by the state-level seroprevalence or estimated proportion of the population ever infected. Abstract: Background: Immune protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be induced by natural infection or vaccination or both. Interaction between vaccine-induced immunity and naturally acquired immunity at the population level has been understudied. Methods: We used regression models to evaluate whether the impact of coronavirus disease 2019 (COVID-19) vaccines differed across states with different levels of naturally acquired immunity from March 2021 to April 2022 in the United States. Analysis was conducted for 3 evaluation periods separately (Alpha, Delta, and Omicron waves). As a proxy for the proportion of the population with naturally acquired immunity, we used either the reported seroprevalence or the estimated proportion of the population ever infected in each state. Results: COVID-19 mortality decreased as coverage of ≥1 dose increased among people ≥65 years of age, and this effect did not vary by seroprevalence or proportion of the total population ever infected. Seroprevalence and proportion ever infected were not associated with COVID-19 mortality, after controlling for vaccine coverage. These findings were consistent in all evaluation periods. Conclusions: COVID-19 vaccination was associated with a sustained reduction in mortality at state level during the Alpha, Delta, and Omicron periods. The effect did not vary by naturally acquired immunity.