The researchers hypothesized that shared characteristics of four seasonal coronaviruses are representative of all human coronaviruses because the four can cause respiratory tract infections but are otherwise dissimilar both biologically and genetically.
The study monitored healthy individuals for 35 years and found that reinfection with the same seasonal coronaviruses frequently occurred 12 months after previous infections. "The researchers looked... to blood samples from 10 healthy individuals enrolled for decades in the Amsterdam Cohort Studies on HIV-1 Infection and AIDS," explained NIH director Dr. Francis Collins in addressing the report.
Results showed that reinfections were seen frequently 12 months after initial infection and, in some cases, as early as six months after.
"The new data show that immunity to other coronaviruses tends to be short-lived, with reinfections happening quite often about 12 months later and, in some cases, even sooner," Collins said.
Therefore, it is important to "proceed carefully and with caution when it comes to long-term immunity, whether achieved through naturally acquired infections or vaccination," he stressed.
It is important to keep three caveats in mind when looking at data from the study, Collins said. The first is that "the researchers tracked antibody levels but didn’t have access to information about actual illness. It’s possible that a rise in antibodies to a particular coronavirus might have provided exactly the response needed to convert a significant respiratory illness to a mild case of the sniffles or no illness at all."
The other two caveats, according to Collins, are that it is unknown to what degree mutational changes of the virus contributed to reinfection, and that the roll of cell-based immunity in fighting off coronavirus infections was not studied but may be significant.