An overview of the Centers for Disease Control and Prevention (CDC) headquarters in Atlanta.
Tami Chappell | Reuters
A new CDC study found that some seniors who apparently recovered from the coronavirus suffered an even worse second infection, indicating that asymptomatic or mild cases may not provide much protection against Covid-19 reinfection.
The study, published Thursday in the Centers for Disease Control and Prevention’s Weekly Morbidity and Mortality Report, looked at two separate outbreaks that occurred three months apart at a specialized nursing facility in Kentucky. Between mid-July and mid-August, 20 residents and five health care professionals tested positive for the virus, according to the study.
The second outbreak between late October and early December was worse: 85 residents and 43 health professionals tested positive for the virus. Among the residents who tested positive during the first outbreak and were still living at the facility, five of them tested positive for the second time more than 90 days apart from the first positive test.
Although Covid-19 reinfections occur, they are generally rare.
Through frequent surveillance after the first outbreak, all five residents had at least four negative outbreaks between outbreaks, suggesting that they could later be reinfected with the virus, according to the study. Reinfection means a person who had Covid-19 recovered and regained it, according to the CDC.
“Exposure history, including timing of roommate infections and new onset of symptoms during the second outbreak, suggest that second positive RT-PCR results represented new infections after patients eliminated the first infection. “wrote Alyson Cavanaugh, one of the researchers who led the study.
Although only two of the five residents experienced mild symptoms during the first outbreak, the five potentially reinfected residents showed signs of illness the second time. The two residents who reported symptoms during the first outbreak “experienced more severe symptoms during the second infectious episode,” according to the study. One resident was hospitalized and later died.
According to the study’s researchers, this was “remarkable” because it suggests the possibility that people who do not show mild symptoms or do not show up during the first infections “do not produce a robust enough immune response to prevent reinfection.” The results “suggest the possibility that the disease may be more severe during a second infection.”
“The results of this study highlight the importance of maintaining public health mitigation and protection strategies that reduce the risk of transmission, even among people with a history of COVID-19 infection,” Cavanaugh wrote.
The study noted some limitations. Because the specimens were not stored, the researchers could not perform genomic sequencing, a laboratory technique that breaks down the genetic code of the virus, to confirm reinfection, the researchers said. In addition, “there are no additional test results to support the initial test result as a true positive” during the first outbreak, they said.
It is believed that the risk of reinfection for the general population is still low, but residents of residences may be particularly at risk given their congregated life and the large number of exposures, according to the study.
“Specialized nursing facilities should use strategies to reduce the risk of SARS-CoV-2 transmission among all residents, including those who have previously been diagnosed with COVID-19,” Cavanaugh wrote.