An overview of the Centers for Disease Control and Prevention (CDC) in Atlanta.
Tami Chappell | Reuters
A new CDC study found that some elderly people who apparently recovered from coronavirus later came in with a second, even more serious 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 Report on Morbidity and Mortality, looked at two separate outbreaks that occurred three months apart at a Kentucky medical unit. Between mid-July and mid-August, 20 residents and five medical staff tested positive for the virus, according to the study.
The second outbreak between late October and early December was more severe – 85 residents and 43 medical staff tested positive for the virus. Of the residents who tested positive during the first outbreak and were still living in the unit, five of them tested positive a second time more than 90 days apart from their first positive test.
Although Covid-19 reinfections do occur, they are generally rare.
Through frequent surveillance after the first outbreak, all five residents had at least four negative tests between outbreaks, suggesting that they would potentially be re-infected with the virus later, the study found. Reinfection means that a person who had Covid-19 recovered and then received it again, according to the CDC.
“The history of exposure, including the timing of roommate infections and the new onset of symptoms during the second outbreak, suggests that the second positive RT-PCR result was new infections after patients apparently cleared the first infection,” Alyson wrote. Cavanaugh, one of the researchers who led the study.
While only two of the five residents showed mild symptoms during the first outbreak, all five potentially reinfected residents showed signs of illness a second time. The two residents who reported symptoms during the first outbreak “showed more severe symptoms during the second infectious episode,” according to the study. A resident was hospitalized and later died.
According to the study’s researchers, this was “noteworthy” because it suggests that people who do not have mild to no symptoms during the first few infections “may not produce a strong enough immune response to prevent reinfection.” The results “suggest the possibility that the disease may be more severe during a second infection.”
The findings of this study highlight the importance of maintaining strategies to mitigate and protect public health that reduce the risk of transmission, even among people with a history of COVID-19 infection, Cavanaugh wrote.
The study mentioned some limitations. Because the specimens were not stored, the researchers were unable to perform genomic sequencing, a laboratory technique that breaks down the virus’s genetic code to confirm reinfection, the researchers said. Also, “there are no additional test results that support the initial test result as 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 nursing homes may be particularly at risk, given their congregated existence and the large number of exposures, according to the study.
“Qualified healthcare facilities should use strategies to reduce the risk of SARS-CoV-2 transmission among all residents, including those with a previous diagnosis of COVID-19,” Cavanaugh wrote.