To date, only a few cases of reinfection with SARS-CoV-2 have been reported. A recent study on the evolution of antibodies among the Icelandic population showed that immunity could last at least up to 4 months.
Work coordinated by the Amsterdam UMC now casts a doubt on longer-lasting immunity. For their study, they have investigated 4 known species of seasonal coronaviruses (HCoV-NL63,-229E, -OC43, and -HKU1). They have used blood samples from the Amsterdam Cohort Studies on HIV-infections. Ten healthy men were selected. Serological tests measured antibody levels on samples periodically taken since 1985.
On average, the 10 individuals have been continuously followed during a period of 20,6 years. Reinfections occurred in total 101 times, without significant differences between the 4 viruses. Reinfections were most frequently seen at 12 months. Virus mutations could not account for this, as they were not observed. The authors suggest that similar reinfection patterns will apply to SARS-CoV-2.
The researchers have used a creative approach to investigate longer time intervals. Also, the group of individuals chosen, although small, is almost ideal if one wishes to avoid sampling bias. The group has no history of SARS-CoV-2; in a way, they have been selected prior to the pandemic. However, the extrapolation of the results with 4 seasonal coronaviruses, causing a common cold, to the new coronavirus seems a bridge too far.
Meanwhile, learning more about reinfections remains key for developing vaccines. Understanding the evolution of specific antibodies with time will help to develop a vaccine which grants prolonged immunity.