Serological follow up of positive SARS-CoV-2 cases.

ABSTRACT

OBJECTIVE: To describe the humoral response in a cohort with mild and asymptomatic SARS-CoV-2 infection previ-ously identified in a community-based serological survey. MATERIALS AND METHODS: This study was an observational follow up of 193 subjects previously identified with positive anti-SARS-CoV-2 antibodies invited for a second test 112 days after the first sampling. All completed a standardized electronic questionnaire. IgM/IgG antibodies were determined using a qualitative IgM/IgG chemiluminescent immunoassay. RESULTS: Among the 193 eligible subjects, a total of 174 (90%) attended the follow-up visit, and their serum samples were tested. Of the samples, 171 (98.3%) were still positive, and 3 (1.7%) were negative. Also, the cut-off index (COI) value of the immunoassay significantly increased from the first to the second test (P <0.001). CONCLUSIONS: Our findings support a sustained humoral response in individuals with mild and asymptomatic SARS-CoV-2 infection up to 112 days after a positive serologic baseline test, accompanied by increasing antibody titers.