Validation and clinical performance of a non-commercial ELISA for SARS-CoV-2 anti-RBD IgA antibodies.

COVID-19 is caused by SARS-CoV-2, first identified in 2019. The Cuban vaccines, Abdala and Mambisa, have demonstrated efficacy in preventing SARS-CoV-2 infection. Immunoglobulin A (IgA) are the main line of defense against pathogens invading the respiratory or digestive tract and its presence in serum can be measured to assess vaccine efficacy. ELISAs are a valuable tool for assessing vaccine immunogenicity. These tests should be validated to ensure their reliability and suitability. The objective of this study was to validate a non-commercial ELISA for the quantification of total anti-RBD IgA in serum samples to support clinical studies. This assay demonstrated high clinical specificity (97.3 %). The accuracy and precision of the assay showed an overall error of less than 20 % at all levels in QCs. Re-evaluation of samples showed a mean difference of less than 30 % in 90.2 % of cases. Anti-RBD IgA titers correlated with viral neutralization titers and percentage inhibition of RBD-ACE2 binding. This assay was found to be highly accurate and reproducible for the quantification of anti-RBD IgA, met the most stringent acceptance criteria and is fit for purpose. It is currently being used to evaluate the immunogenicity of the Abdala and Mambisa vaccines.