ABSTRACT
PURPOSE: Studies on the immune responses to severe acute respiratory syndrome coronavirus 2 vaccines are necessary to evaluate the ongoing vaccination programs by correlating serological response data and clinical effectiveness data. We performed a longitudinal immunological profiling of health care workers vaccinated with mRNA-1273 (Moderna, Cambridge, MA, USA). Half of these vaccinees had experienced a mild coronavirus disease 2019 (COVID-19) infection in the spring of 2020 ("COVID-recovered" cohort), whereas the other half of the vaccinees had no previous COVID-19 infection ("COVID-naive" cohort). MATERIALS AND METHODS: Serum was drawn at multiple time points and subjected to assays measuring anti-Spike immunoglobulin G (IgG), avidity of anti-Spike IgG, avidity of anti-receptor binding domain (RBD) IgG, virus neutralizing activity, and interferon-γ release from stimulated lymphocytes. RESULTS: Between both cohorts and within each cohort, we found remarkable inter-individual differences regarding cellular and humoral immune responses to the Moderna mRNA-1273 vaccine. CONCLUSION: First, our study indicates that the success of mRNA-1273 vaccinations should be verified by serological assays in order to identify "low-responders" to vaccination. Second, the kinetics of anti-S IgG and neutralizing activity correlate well with clinical effectiveness data, thus explaining incipient protection against infection 2 weeks after the first dose of mRNA-1273 in COVID-naive vaccinees. Third, our IgG-avidity data indicate that this incipient protection is mediated by low-avidity anti-RBD IgG and low-avidity anti-S IgG.
ABSTRACT
Current studies focus on cellular and humoral immunity induced by novel SARS-CoV-2 vaccines. Non-responders to vaccinations are not uncommonly encountered in clinical medicine (e.g. in the field of hepatitis B). Whereas vaccine-induced humoral immunity against SARS-CoV-2 is compromised by emerging Variants of Concern (VOCs), cellular immunity against SARS-CoV-2 is emerging as resilient against VOCs. Thus commercially available test kits for diagnostic laboratories designed to evaluate cellular immune responses to SARS-CoV-2 are urgently needed. Here we evaluated the novel QuantiFERON SARS-CoV-2 assay (Qiagen) measuring INF-É£ release induced by two spike-derived peptide pools (Ag1 and Ag2) in a cohort of health care workers vaccinated with the mRNA-1273 vaccine and confirmed humoral response. Our study indicates the usefulness of this novel assay for routine laboratories to evaluate cellular immunity against SARS-CoV-2 in response to mRNA-1273 vaccination.