Image of Sunil Parikh, M.D., MPH; Image credit: Yale University
Sunil Parikh, M.D., MPH; Image credit: Yale University

The prevalence of repeat positive COVID-19 tests among nursing home residents suggests true reinfections — and more quickly waning immunity — in these elders, according to a study across all Connecticut facilities.

The state was able to conduct rapid and frequent testing of nursing home residents by mid-May 2020. This allowed investigators from Yale University and the Connecticut Department of Public Health to examine nine months of testing data gathered before COVID-19 vaccines were available. 

Fully 2.6% of residents in the state’s 212 nursing homes had one or more repeat positive SARS-CoV-2 PCR tests, they found. This was significantly more than older community dwellers and younger adults. What’s more, these repeat positives occurred as early as 90 days after an initial positive test, the researchers reported.

The patterns of test results were surprising — even among nursing home residents, who are typically older and more frail than their community-dwelling peers, Sunil Parikh, M.D., MPH, said.

Notably, 12.6% of residents who had a repeat positive test died soon after (a median eight days after the repeat positive test). In addition, 80% of these residents had one or more intervening negative tests. This suggested that the infections were true reinfections, and that the second infections were more deadly, the investigators said.

“This was an early clue as to the less robust and waning immunity that may be seen in this vulnerable population following natural SARS-CoV-2 infection,” Parikh, the study’s lead author, concluded.

The results have important implications for assessing the ongoing risk of long-term care residents, he and his colleagues said.

“Taken together, our data support that repeat testing should continue in individuals living in nursing homes once 90 days have elapsed since their initial positive SARS-CoV-2 test,” they wrote.

The study was published in The Lancet Regional Health – Americas.