A COVID-19 outbreak at a Kentucky nursing home was caused by a si…

A COVID-19 outbreak at a Kentucky nursing home was caused by a single unvaccinated employee, according to a new Centers for Disease Control and Prevention study, but the residents and employees who were vaccinated were much better protected.
The outbreak was linked to dozens of infections in both employees and residents, including in 22 residents and workers who had already been vaccinated. The virus was introduced from a single employee who was unvaccinated and symptomatic.
However, attack rates were three to four times as high among unvaccinated residents and employees as among those who were vaccinated, and the vaccinated staff and residents were significantly less likely to experience symptoms or require hospitalization.
During the outbreak, 46 COVID-19 cases were identified, CDC said, including cases in 26 residents, where 18 were fully vaccinated, and 20 health care personnel, where four were vaccinated.
One vaccinated resident, who had previously been infected 300 days earlier, became reinfected during the outbreak and died. Two unvaccinated residents also died. 
The low rate of breakthrough infections, and the fact that most of the breakthrough infections were asymptomatic, underscores the importance of vaccinating nursing home residents and staff.
The coronavirus is most likely to be introduced to a nursing home through an infected staff member who regularly enters and leaves the facility. In the Kentucky nursing home CDC examined, 90 percent of the 83 residents were vaccinated, but only half of the 116 staff were at the time of the outbreak in March.
Low acceptance of vaccination among nursing home workers has been a challenge nationwide, and could increase the likelihood of COVID-19 introduction and transmission within a facility, the CDC said.
Vaccination of workers and residents “is critical to reduce the risk for SARS-CoV-2 introduction, transmission, and severe outcomes” in nursing facilities, the CDC said.  
The outbreak involved the R.1 variant of the virus, which the CDC does not list as a variant of concern, but still contains multiple mutations in the spike protein that could make vaccines less effective.
The Pfizer-BioNTech vaccine showed effectiveness of 66 percent for residents against infection, and 75.9 percent for employees. 
CDC acknowledged both numbers are lower than those reported from Israels national vaccination program. That could be due to reduced protection against the R.1 variant, but could also be due to a small sample size and the higher exposure risk associated with an outbreak in a congregate setting
Still, CDC said vaccinated residents and staff were 87 percent less likely to have symptomatic COVID-19 compared with those who were unvaccinated.
Meanwhile, a separate study released concurrently of Chicago-area nursing homes found that among the 627 people with COVID-19 infections across 75 nursing homes, only 22 infections were found in people who had been vaccinated, and no facility-associated secondary transmission occurred. 
Nearly two thirds of those breakthrough infections were asymptomatic. Still, two residents were hospitalized because of COVID-19, and one died. 
CDC said the study in Chicago shows nursing homes still need to follow recommended infection and control practices, and promote high vaccination coverage among residents and staff members.