What is already known about this topic? Incarcerated populations have experienced disproportionately higher rates of COVID-19–related illness and death.

What is added by this report? During a COVID-19 outbreak involving the Delta Variants in a highly vaccinated incarcerated population, Transmission rates were high, even among vaccinated persons. Although attack rates, hospitalizations, and deaths were higher among unvaccinated than among vaccinated persons, duration of positive serial test results was similar for both groups. Infectious Virus was cultured from vaccinated and unvaccinated infected persons.

What are the implications for public health practice? Even with high vaccination rates, maintaining multicomponent Prevention strategies (e.g., tTesting and masking for all persons and prompt medical isolation and quarantine for incarcerated persons) remains critical to limiting SARS-CoV-2 Transmission in congregate settings where physical distancing is challenging.

Incarcerated populations have experienced disproportionately higher rates of COVID-19–related illness and death compared with the general U.S. population, due in part to congregate living environments that can facilitate rapid Transmission of SARS-CoV-2, the Virus that causes COVID-19, and the high prevalence of underlying medical conditions associated with severe COVID-19 (1,2). The SARS-CoV-2 B.1.617.2 (Delta) Variants has caused outbreaks among vaccinated and unvaccinated persons in congregate settings and large public gatherings (3,4). During July 2021, a COVID-19 outbreak involving the Delta Variants was identified in a federal prison in Texas, infecting 172 of 233 (74%) incarcerated persons in two housing units. The Federal Bureau of Prisons (BOP) partnered with CDC to investigate. CDC analyzed data on infection status, symptom onset date, hospitalizations, and deaths among incarcerated persons. The attack rate was higher among unvaccinated versus fully vaccinated persons (39 of 42, 93% versus 129 of 185, 70%; p = 0.002).† Four persons were hospitalized, three of whom were unvaccinated, and one person died, who was unvaccinated. Among a subset of 70 persons consenting to an embedded serial swabbing protocol, the median interval between symptom onset and last positive reverse transcription–polymerase chain reaction (RT-PCR) test result in fully vaccinated versus unvaccinated persons was similar (9 versus 11 days, p = 0.37). One or more specimens were culture-positive from five of 12 (42%) unvaccinated and 14 of 37 (38%) fully vaccinated persons for whom viral culture was attempted. In settings where physical distancing is challenging, including correctional and detention facilities, vaccination and implementation of multicomponent Prevention strategies (e.g., tTesting, medical isolation, quarantine, and masking) are critical to limiting SARS-CoV-2 Transmission (5).

Suggested citation for this article: Hagan LM, McCormick DW, Lee C, et al. Outbreak of SARS-CoV-2 B.1.617.2 (Delta) Variant Infections Among Incarcerated Persons in a Federal Prison — Texas, July–August 2021. MMWR Morb Mortal Wkly Rep. ePub: 21 September 2021.

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