9/5/2023 0 Comments Covid 19 omicron reinfection![]() More recent data from household studies of Omicron variant transmission support that vaccination may reduce infectiousness, although they are often limited in capturing detailed aspects of the transmission environment and accounting for interaction with prior infection 11, 12, 13. ![]() These data were predominately among individuals immunized only with primary series doses 6, 7, 8, 9, 10. Before the Omicron variant, available data on the infectiousness of SARS-CoV-2 breakthrough infections in vaccinated individuals was mixed there was evidence to support reduced infectiousness of breakthrough infections in household studies and through study of viral kinetics 6, 7, 8, although other studies have found no difference in the infectiousness of primary and breakthrough SARS-CoV-2 infections 9, 10. There are limited data on the infectiousness of breakthrough SARS-CoV-2 infections in vaccinated individuals and reinfections with the Omicron variant, especially in high-risk transmission settings, such as prisons. Determining the impact of vaccination, including booster doses, and prior infection on the infectiousness of individuals with Omicron variant infections remains necessary to understand transmission dynamics of these variants. After the emergence of the highly infectious Omicron variant in December 2021, the United States observed the largest surge in Coronavirus Disease 2019 (COVID-19) cases to date 5. Although the early pandemic was characterized by infections in fully susceptible individuals, SARS-CoV-2 breakthrough infections among vaccinated individuals and reinfections among previously infected individuals are now increasingly frequent 2, 3, 4. Transmission dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have shifted over the course of the pandemic due to widespread vaccination, natural infection and emergence of novel variants 1. This study underscores benefit of vaccination to reduce, but not eliminate, transmission. These findings suggest that, although vaccinated and/or previously infected individuals remain highly infectious upon SARS-CoV-2 infection in this prison setting, their infectiousness is reduced compared to individuals without any history of vaccination or infection. Receipt of booster doses and more recent vaccination further reduced infectiousness among vaccinated cases. In adjusted analyses, we estimated that any vaccination, prior infection alone and both vaccination and prior infection reduced an index case’s risk of transmitting infection by 22% (6–36%), 23% (3–39%) and 40% (20–55%), respectively. Analyzing SARS-CoV-2 surveillance data from December 2021 to May 2022 across 35 California state prisons with a predominately male population, we estimate that unvaccinated Omicron cases had a 36% (95% confidence interval (CI): 31–42%) risk of transmitting infection to close contacts, as compared to a 28% (25–31%) risk among vaccinated cases. Here we show that both vaccine-derived and naturally acquired immunity independently reduce the infectiousness of persons with Omicron variant SARS-CoV-2 infections in a prison setting. Such infections highlight a broader need to understand the contribution of vaccination, including booster doses, and natural immunity to the infectiousness of individuals with SARS-CoV-2 infections, especially in high-risk populations with intense transmission, such as in prisons. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) breakthrough infections in vaccinated individuals and reinfections in previously infected individuals have become increasingly common. ![]()
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