The delta coronavirus variant revealed its full potential in a Texas federal prison during a monthlong outbreak that infected 172 of 233 (74%) incarcerated people in just two neighboring housing units, an investigation published Tuesday found.
The Federal Bureau of Prisons and the Centers for Disease Control and Prevention learned the variant’s “attack rate” was higher among unvaccinated prisoners, infecting 39 of 42 people (93%), compared to vaccinated prisoners, infecting 129 of 185 (70%), during the July outbreak.
However, officials found the amount of time prisoners continued to test positive after first showing symptoms was “comparable” regardless of vaccination status. They also learned both vaccinated and unvaccinated prisoners carried infectious virus particles in their respiratory samples, all of which comprised the delta variant, meaning both groups could infect others.
Still, four people were hospitalized, only one of whom was vaccinated. One unvaccinated person died in a hospital after receiving mechanical ventilation, underscoring the role vaccinations play in preventing severe COVID-19 illness and death, especially in crowded living conditions such as prisons that can fuel coronavirus spread.
The CDC also said its findings highlight the importance of other preventive measures in addition to vaccines such as mask wearing, proper isolation of infected people, and frequent testing to prevent and slow COVID-19 outbreaks.
The prison and the city where it’s located were not named. COVID-19 vaccination was optional for both staff and prisoners.
At least nine staff members, four of whom worked directly in the affected housing units, contracted COVID-19 during the outbreak, but researchers warn the number could be higher given testing was not mandatory for employees. Records show nearly two-thirds of staff at the prison were unvaccinated at the time.
Genetic sequencing revealed a “single viral lineage,” suggesting one person, likely a staff member or other prisoner transferred from another facility, introduced the coronavirus into the prison. The findings are in line with other studies and investigations that have found incarcerated populations in the U.S. have experienced “disproportionately higher rates” of coronavirus infection, illness and death.
As of Sept. 21, there have been more than 424,00 COVID-19 cases among incarcerated people in U.S. prisons, including 2,590 who have died, according to the COVID Prison Project that tracks coronavirus activity from all 50 states, Puerto Rico, the Federal Bureau of Prisons and Immigration and Customs Enforcement. More than 122,000 prison staff members have contracted COVID-19, including 209 who have died.
The investigation showed a higher attack rate among prisoners who were vaccinated four or more months prior to the outbreak (89%) compared to those who got their shots two weeks to two months before (61%). The virus’s attack rate was also higher among people who got the Pfizer-BioNTech vaccine (85%) than those who got the Moderna shot (54%).
Overall, fully vaccinated prisoners who previously had the coronavirus were less likely to be infected during the July outbreak. The CDC says more research is needed to better understand what roles natural immunity versus vaccine-induced immunity played in this scenario.
The affected housing units were “interconnected” and “operated as a single cohort.” They had cells without doors that housed two to 10 people each.
Before the outbreak, prisoners were able to move freely in between the units and mingled during meals, recreation and work, with no contact with other incarcerated people in other units. But after coronavirus cases emerged, one unit housed infected people and the other non-infected people.
Assigned staff, on the other hand, “rotated between these two units and to other units on the basis of daily staffing needs.”
Prisoners were required to wear masks in common areas, participate in daily activities only with others from their housing units, and sleep “head-to-toe.” Staff members were also required to wear masks and were subject to mandatory daily COVID-19 symptoms screenings and temperature checks.