Evaluation of residual humoral immune response against SARS-CoV-2 by a surrogate virus neutralization test (sVNT) 9 months after BNT162b2 primary vaccination

• Published in: Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy Vol. 29; no. 6; pp. 624 - 627
• Main Authors: Pezzati, Laura, Milazzo, Laura, Carrozzo, Giorgia, Kullmann, Cristina, Oreni, Letizia, Beltrami, Martina, Caronni, Stefania, Lai, Alessia, Caberlotto, Livio, Ottomano, Cosimo, Antinori, Spinello, Ridolfo, Anna Lisa
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.06.2023; Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd
• Subjects: Antibodies, Neutralizing; Antibodies, Viral; BNT162 Vaccine; COVID-19 - prevention & control; COVID-19 Vaccines; Cross-Sectional Studies; Healthcare workers; Humans; Immune response; Immunity, Humoral; Immunoglobulin G; Neutralization Tests; Neutralizing capacity; SARS-CoV-2; Vaccination; SARS-CoV-2; Neutralizing capacity; Healthcare workers; Immune response; Vaccination
• ISSN: 1341-321X; 1437-7780; 1437-7780
• DOI: 10.1016/j.jiac.2023.03.002

The humoral response to SARS-CoV-2 vaccination has shown to be temporary, although may be more prolonged in vaccinated individuals with a history of natural infection. We aimed to study the residual humoral response and the correlation between anti-Receptor Binding Domain (RBD) IgG levels and antibody neutralizing capacity in a population of health care workers (HCWs) after 9 months from COVID-19 vaccination. In this cross-sectional study, plasma samples were screened for anti-RBD IgG using a quantitative method. The neutralizing capacity for each sample was estimated by means of a surrogate virus neutralizing test (sVNT) and results expressed as the percentage of inhibition (%IH) of the interaction between RBD and the angiotensin-converting enzyme. Samples of 274 HCWs (227 SARS-CoV-2 naïve and 47 SARS-CoV-2 experienced) were tested. The median level of anti-RBD IgG was significantly higher in SARS-CoV-2 experienced than in naïve HCWs: 2673.2 AU/mL versus 610.9 AU/mL, respectively (p <0.001). Samples of SARS-CoV-2 experienced subjects also showed higher neutralizing capacity as compared to naïve subjects: median %IH = 81.20% versus 38.55%, respectively; p <0.001. A quantitative correlation between anti-RBD Ab and inhibition activity levels was observed (Spearman's rho = 0.89, p <0.001): the optimal cut-off correlating with high neutralization was estimated to be 1236.1 AU/mL (sensitivity 96.8%, specificity 91.9%; AUC 0.979). Anti-SARS-CoV-2 hybrid immunity elicited by a combination of vaccination and infection confers higher anti-RBD IgG levels and higher neutralizing capacity than vaccination alone, likely providing better protection against COVID-19.