SNF Cases Raise Questions About How Long COVID-19 Immunity Lasts

One of the most critical unanswered questions during the COVID-19 pandemic is how long immunity lasts in patients recovered from SARS-CoV-2 infection. A new CDC report from Kentucky has raised concerns because it shows that five nursing home residents had recurrence of COVID-19 and had more severe cases the second time compared to the first. Here are more details.

FRANKFURT, KY – While reinfection with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is believed to be rare, no one is sure how common it is or how long immunity lasts after recovery from COVID-19 infection.

Public health officials expressed concern after reports of suspected recurrent SARS=CoV-2 infection in a Kentucky skilled nursing facility during the July-November 2020 outbreak. The cases were reported in the Morbidity & Mortality Weekly Report, published by the national Centers for Disease Control and Prevention.

“Case reports of reinfection with SARS-CoV-2 exist; however, data are limited as to the frequency and outcomes of reinfection,” according to authors from the CDC and Kentucky Department for Public Health.

The article describes how five residents of a skilled nursing facility received positive SARS-CoV-2 nucleic acid test results in two separate COVID-19 outbreaks separated by 3 months.

“Residents received at least four negative test results between the two outbreaks, suggesting the possibility of reinfection,” according to the report. “Severity of disease in the five residents during the second outbreak was worse than that during the first outbreak and included one death.”

The authors recommend that skilled nursing facilities use strategies to reduce the risk for SARS-CoV-2 transmission among all residents, including those who have previously had a COVID-19 diagnosis. Vaccination of residents and health care personnel in this setting is particularly important to protect residents, they emphasize.

Based on exposure history, including the timing of roommates’ infections and the new onset of symptoms during the second outbreak, the report posits that the second positive RT-PCR results represented new infections after the patients had apparently cleared the first infection.

“The finding that all five patients with recurrent COVID-19 had either asymptomatic or mildly symptomatic courses during their first infections is noteworthy, suggesting the possibility that asymptomatic or mildly symptomatic initial infections do not produce a sufficiently robust immune response to prevent reinfection,” the authors write. “The patients with recurrent illness ranged in age from 67 to 99 years; a decline in immune system function with aging is well-documented, but little scientific evidence is available to date regarding whether or how an aging immune system might affect response to initial SARS-CoV-2 infection, likelihood of reinfection upon new exposure, and illness severity associated with reinfection.”

They also suggest that the absence of symptoms in three of five patients during the initial episode could support the argument that the test results during the first outbreak were false positives, although they add that up to 40%–50% of infections are asymptomatic and that, in these cases, “Ct values for the positive test results in the first outbreak were within the cutoff for limit of detection, suggesting virus titers consistent with infection.”

The report adds that the findings “support the possibility of reinfection in this population, though more definitive evidence with genomic sequencing is missing. The findings also suggest the possibility that disease can be more severe during a second infection.”

The setting also might have influenced the outcomes, the authors advise, writing, “Reinfection risk to the general population is suspected to be low, but SNF residents might have higher risk for new exposures, given the congregate nature of these settings and ongoing interactions with HCP and other residents.”

Based on the study, they emphasize that testing and cohorting practices in SNFs should not assume that residents infected more than 90 days earlier remain immune to COVID-19.

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