In a new study, published Sept. 14 in the journal Nature Medicine, scientists monitored 10 individuals for more than 35 years to determine how often they became infected with the four known seasonal coronaviruses. Since these viruses — known as HCoV-NL63, HCoV-229E, HCoV-OC43 and HCoV-HKU1 — either cause mild symptoms of the common cold or no symptoms at all, the team periodically screened the participants' blood for antibodies to spot new cases of infection.
When blood samples show an increase in the number of antibodies targeting a specific virus, as compared with prior samples, that means that the person's immune system is fighting off a new infection. The researchers determined how steep this shift in antibody levels had to be to constitute a confirmed infection, rather than random fluctuation.
"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," Dr. Francis Collins, director of the National Institutes of Health (NIH), wrote in a commentary about the research. In a few instances, reinfections occurred as early as six months and nine months after a prior infection, the study authors found.
The 10 study participants were all part of the Amsterdam Cohort Studies (ACS) on HIV-1 infection and AIDS, a study of the prevalence, incidence and risk factors for HIV infection that began in the 1980s. The participants, all HIV-negative, gave blood samples every three to six months throughout the study, providing 513 samples in total.
