An unvaccinated worker started a case in a US nursing home where the majority of residents were immunized.

An unvaccinated health care worker initiated a case of Covid-19 in a nursing home in Kentucky where the vast majority of residents had been vaccinated, leading to dozens of infections, including 22 cases among residents and workers already full vaccination, new study. reported Wednesday.

The majority of those infected with the coronavirus despite being vaccinated did not develop symptoms or need to go to hospital, but one vaccinated person, who lived in the hospital, died. nursing home, according to the study released by the Centers for Disease Control and Prevention.

In total, 26 facility residents were infected, including 18 who were vaccinated, and 20 healthcare personnel were infected, including four who had been vaccinated. Two unvaccinated residents also died.

The report underlines the importance of vaccinating nursing home residents and healthcare workers entering and exiting the sites, the authors said. While 90 percent of the 83 residents in the Kentucky nursing home were vaccinated, only half of the 116 employees were vaccinated when the outbreak was reported in March this year.

The study, released alongside one relating to Chicago nursing homes, underlined the importance of maintaining measures such as the use of protective gear, infection control protocols and routine testing, no matter the level of vaccination rates. The rise of virus variants has also heightened concerns.

Vaccine resistance has been steepest among nursing home staff nationwide, and low vaccine uptake rates increase the likelihood of facility outbreaks, according to the authors, a team of researchers from the CDC and the Kentucky department of public health .

“In order to protect the residents of skilled nursing facilities, it is essential that healthcare providers, as well as residents of skilled nursing facilities, are vaccinated,” wrote the authors of a Kentucky study.

The outbreak involved a variant of the virus that has multiple mutations in the spike protein, of the kind that makes the vaccines less effective. Vaccinated residents and healthcare workers at the Kentucky facility were less likely to become infected than those who had not been vaccinated, and were much less likely to develop symptoms. The study estimated that the vaccine, identified as Pfizer-BioNTech, showed 66 percent efficacy for residents and 75.9 percent for workers, and that they were 86 percent to 87 percent effective in protecting against symptomatic disease .

In the case of Kentucky, the virus variant is not on the CDC’s list of those considered to be variations of concern or interest. But, the study’s authors point out, the variant has several mutations of importance: D614G, which shows evidence of increased transmissibility; E484K in the hinge protein receptor binding domain, also found in B.1.351, the first recognized variant in South Africa, and P.1. from Brazil; and W152L, which may reduce the efficacy of neutralizing antibodies.

In Chicago, meanwhile, routine screening of nursing home residents and staff members identified 627 coronavirus infections at 78 skilled nursing facilities in the city in February, but only 22 were found in previously vaccinated individuals full. Two-thirds of cases in the vaccinated individuals were disproportionate, the report found, but two residents were hospitalized, and one died.

The authors of the Chicago study reported that their findings indicate that nursing homes should continue to follow recommended infection control practices, such as isolation and quarantine, use of personal protective equipment and perform routine tests, regardless of vaccination status.

They also stressed the importance of “maintaining high vaccination coverage among residents and staff” in order to “reduce transmission opportunities within facilities and exposure among people who may not have achieved protective immunity after vaccination.”