Antibodies can be measured in a sensitive and specific manner, providing an archive that reflects recent or previous infection. If maintained at sufficiently high levels, antibodies can rapidly block infection on reexposure, conferring long-lived protection.…The New England Journal of Medicine, The Power of Antibody-Based Surveillance, Galit Alter, Ph.D., and Robert Seder, M.D., 2021
Contrary to recent reports suggesting that SARS-CoV-2 RNA testing alone, in the absence of antibodies, will be sufficient to track and contain the pandemic, the cost, complexity, and transient nature of RNA testing for pathogen detection render it an incomplete metric of viral spread at a population level.
In midsummer 2020, studies emerged pointing to rapid waning of antibody immunity with reports across the globe suggesting that antibody responses were inversely correlated to disease severity even suggesting that asymptomatic infection could occur without seroconversion. Consistently, in a month-long study, antibody titers were noted to wane both in patients with mild infection and in those with severe infection, which raised the possibility that humoral immunity to this coronavirus may be very short-lived.
The data reported by Stefansson and colleagues point to the utility of antibody assays as highly cost-effective alternatives to PCR testing for population-level surveillance, which is critical to the safe reopening of cities and schools, and as biomarkers and possible effectors of immunity.