In addition to virus exposure, there is an urgent need to better understand the levels and duration of protective immunity for public health considerations. Research in saliva has identified that SARS-CoV-2 antibody testing could serve as a sensitive and specific serum alternative for large scale immune-surveillance studies (1). Importantly, IgG in saliva is derived from serum, so specificity and reactivity of salivary IgG directly reflects serum IgG reactivity, making oral fluid an attractive alternative sample to blood for serological studies (2, 3).

Current research has shown that antibody levels decrease in the serum of COVID-19 patients over time (4) and vary depending on disease severity. In fact, a higher number of asymptomatic participants become seronegative at 60 days indicating a true decline over a 2-month period rather than an artifact of assay performance. Due to this, the current assay has been benchmarked to a serum specific anti-N protein assay instead of PCR assay results.