More than a quarter of fully vaccinated residents of a Kentucky nursing home still got a rare variant of COVID-19, according to one of the two new Centers for Disease Control and Prevention (CDC) studies.
The studies examine how the coronavirus ripped through skilled nursing facilities in Chicago and Kentucky.
In Chicago, only about four percent of the infections were among the people who had their shot.
But a rare variant in a single facility in Kentucky made vaccines only about 66 percent effective for residents and 76 percent effective for staff – much lower than the 94 or 95 percent efficacy found in clinical trials for injections made by Moderna and Pfizer, respectively.
The two studies emphasize that vaccines work well, but do not provide guaranteed protection, especially when dangerous variants are in circulation.
None of the three vaccines approved in the US were 100 percent effective in clinical trials, meaning so-called ‘breakthrough’ infections are to be expected.
In a Kentucky nursing home, 18 vaccinated residents (black stripes) were infected with a rare, more contagious Covid variant, as were four vaccinated nursing home workers (light blue)
Only four percent of the fully vaccinated staff and the (black) residents of 78 nursing homes in Chicago became infected
In Chicago, there were outbreaks of COVID-19 in 75 of 78 nursing homes between December 2020 and March 2021.
During that period, there were 627 cases of COVID-19 in the facilities.
Of these, 22 were considered breakthrough infections, occurring in 15 of the homes. Twelve of these were residents – most of whom were 60 years of age or older – and 10 were employees.
That represents only about four percent of all nursing home cases in the Chicago period, suggesting the shots were about 96 percent effective overall.
However, vaccination coverage varied widely from nursing home to nursing home.
Some had vaccination rates as low as 18 percent, while 96 percent of residents and staff were vaccinated at others.
The Kentucky nursing home was hit by R1, a rare Covid variant not considered of interest or concern by the CDC. It represents only 1.1% of the US infections
The majority of people who contracted the coronavirus after vaccination never developed symptoms (64 percent).
Five of them developed symptoms, but only mild ones. Two of the nursing home residents were hospitalized for COVID-19 after breakthrough infections, and one of them eventually died.
Overall, the Chicago vaccines performed about as expected, and no one who developed a breakthrough infection passed the virus in a secondary transmission.
Even in the face of a worrying variant, vaccines were still very effective, preventing about 87 percent of infections in a Kentucky nursing home.
But the higher number of breakthrough cases there showed how current and future variants could escape the vaccines.
More than 90 percent of residents and just over half of the nursing home staff had been fully vaccinated against COVID-19 by March.
In total, 26 residents and 20 employees of the facility – where 83 residents were cared for by 116 employees – developed COVID-19.
Twenty-two of these were breakthrough infections in humans who had received both doses of vaccines.
Genome sequencing of a virus sample revealed that a variant known as R1 was driving the outbreak.
R1 is not considered a variant of concern or interest by the CDC, which means it is not considered a major threat.
But it does have three mutations in its spike protein – the part of the virus that allows it to break into human cells – which can make it more contagious and less affected by antibodies to the coronavirus caused by previous infection or vaccines.
According to the CDC’s tracking, about 1.1 percent of all U.S. infections are caused by R1, which is slightly more than caused by the South African variety, B3151, and slightly less than the Brazilian P1 variety.
The R1 variant hit vaccinated elderly people in the facility at an alarming rate.
More than a quarter of the fully vaccinated residents became infected, as did more than seven percent of the staff.
And according to the CDC study, four people may have been reinfected and developed symptoms with their second attacks of the virus.
The risks of developing the infection were still about three times lower for people vaccinated compared to those who had not been vaccinated.
And vaccines prevented 87 percent of staff from developing Covid symptoms or being hospitalized for the infection, and prevented 94 percent of hospital admissions among residents.
In comparison, four out of six nursing home residents who had not been vaccinated and had fallen for the coronavirus had to be hospitalized.
However, one vaccinated resident died of COVID-19, as did two unvaccinated residents.
Overall, the vaccines were about 66 percent effective at protecting residents, older people with generally weaker immune responses, and 76 percent of staff against infection.
The CDC authors note that the low vaccination coverage among staff members likely allowed the dangerous variant – which had never before been identified in Kentucky – to enter and spread through the facility.