SARS-CoV-2 Serologic Assay Needs for the Next Phase of the US COVID-19 Pandemic Response

BACKGROUND: There is a need for validated and standardized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) quantitative immunoglobulin G (IgG) and neutralization assays that can be used to understand the immunology and pathogenesis of SARS-CoV-2 infection and support the coronavirus disease 2019 (COVID-19) pandemic response. METHODS: Literature searches were conducted to identify English language publications from peer-reviewed journals and preprints from January 2020 through November 6, 2020. Relevant publications were reviewed for mention of IgG or neutralization assays for SARS-CoV-2, or both, and the methods of reporting assay results. RESULTS: Quantitative SARS-CoV-2 IgG results have been reported from a limited number of studies; most studies used in-house laboratory-developed tests in limited settings, and only two semiquantitative tests have received US Food and Drug Administration (FDA) Emergency Use Authorization (EUA). As of November 6, 2020, there is only one SARS-CoV-2 neutralization assay with FDA EUA. Relatively few studies have attempted correlation of quantitative IgG titers with neutralization results to estimate surrogates of protection. The number of individuals tested is small compared with the magnitude of the pandemic, and persons tested are not representative of disproportionately affected populations. Methods of reporting quantitative results are not standardized to enable comparisons and meta-analyses. CONCLUSIONS: Lack of standardized SARS-CoV-2 quantitative IgG and neutralization assays precludes comparison of results from published studies. Interassay and interlaboratory validation and standardization of assays will support efforts to better understand antibody kinetics and longevity of humoral immune responses postillness, surrogates of immune protection, and vaccine immunogenicity and efficacy. Public–private partnerships could facilitate realization of these advances in the United States and worldwide.