We report the emergency development and application of a robust serologic test to evaluate acute and convalescent antibody responses to SARS-CoV-2 in Argentina. The assays, COVIDAR
IgG and
IgM, which were produced and provided for free to health authorities, private and public health institutions and nursing homes, use a combination of a trimer stabilized spike
protein and the receptor binding domain (RBD) in a single
enzyme-linked
immunosorbent assay (ELISA) plate. Over half million tests have already been distributed to detect and quantify
antibodies for multiple purposes, including assessment of immune responses in hospitalized patients and large seroprevalence studies in neighborhoods, slums and health care workers, which resulted in a powerful tool for asymptomatic detection and policy making in the country. Analysis of antibody levels and longitudinal studies of symptomatic and asymptomatic
SARS-CoV-2 infections in over one thousand patient samples provided insightful information about
IgM and
IgG seroconversion time and kinetics, and
IgM waning profiles. At least 35% of patients showed seroconversion within 7 days, and 95% within 45 days of symptoms onset, with simultaneous or close sequential
IgM and
IgG detection. Longitudinal studies of asymptomatic cases showed a wide range of antibody responses with median levels below those observed in symptomatic patients. Regarding convalescent plasma applications, a protocol was standardized for the assessment of end point
IgG antibody titers with COVIDAR with more than 500 plasma donors. The protocol showed a positive correlation with
neutralizing antibody titers, and was used for clinical trials and
therapies across the country. Using this protocol, about 80% of convalescent donor plasmas were potentially suitable for
therapies. Here, we demonstrate the importance of providing a robust and specific serologic assay for generating new information about antibody kinetics in infected individuals and mitigation policies to cope with pandemic needs.