A COVID-19 outbreak at a Kentucky nursing home was caused by a single unvaccinated employee, according to a new study by the Centers for Disease Control and Prevention, but residents and employees who were vaccinated were much better protected.
The outbreak was linked to dozens of infections in both employees and residents, including 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 higher among unvaccinated residents and employees than among those who were vaccinated, and vaccinated staff and residents were significantly less likely to show symptoms or to require hospitalization.
During the outbreak, 46 COVID-19 cases were identified, the CDC said, including cases in 26 residents, where 18 were fully vaccinated and 20 medical staff, where four were vaccinated.
A vaccinated resident, who had previously been infected 300 days earlier, was re-infected during the outbreak and died. Two unvaccinated residents also died.
The low rate of infections detected and the fact that most of the infections discovered were asymptomatic, underline the importance of vaccinating residents and nursing home staff.
Coronavirus is most likely to be introduced into a nursing home by an infected staff member who regularly enters and leaves the unit. At the Kentucky health care home in CDC, 90 percent of the 83 residents were vaccinated, but only half of the 116 employees were at the time of the March outbreak.
Low acceptance of vaccination among nursing home workers has been a national challenge and could increase the likelihood of COVID-19 being introduced and transmitted in a unit, the CDC said.
Vaccination of workers and residents “is essential to reduce the risk of the introduction, transmission and severe outcomes of SARS-CoV-2” in health care institutions, the CDC said.
The outbreak involved variant R.1 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 an efficiency of 66% for residents against infection and 75.9% for employees.
The CDC acknowledged that both numbers are lower than those reported in Israel’s national immunization program. This may be due to the reduced protection against variant R.1, but may also be due to a smaller sample size and a higher risk of exposure associated with an outbreak in a common framework.
However, the CDC said that residents and vaccinated staff were 87% less likely to have symptomatic COVID-19 than those who were not vaccinated.
Meanwhile, a separate study published concurrently with nursing homes in the Chicago area found that of the 627 people with COVID-19 infections in 75 nursing homes, only 22 infections were found in people who were vaccinated. and no secondary transmission associated with the facility took place.
Nearly two-thirds of those infections discovered were asymptomatic. However, two residents were hospitalized due to COVID-19 and one died.
The CDC said the Chicago study shows that nursing homes should follow recommended infection and control practices and promote high vaccination coverage among residents and staff members.