Assessment of the Humoral Immune Response Following COVID‐19 Vaccination in Healthcare Workers: A One Year Longitudinal Study

• Main Authors: Chiriac, D. (Author), Chivu‐economescu, M. (Author), Cirstoiu, C. (Author), Cornienco, A.M (Author), David, A. (Author), Diaconu, C.C (Author), Florescu, S.A (Author), Furtunescu, F.L (Author), Gatea, A. (Author), Grancea, C. (Author), Iancu, L.S (Author), Ilie, C. (Author), Leustean, M. (Author), Malciolu, S. (Author), Matei, L. (Author), Petru, R. (Author), Pistol, A. (Author), Pop, C.S (Author), Popescu, C.P (Author), Radu, I. (Author), Rafila, A. (Author), Ruta, S.M (Author), Strambu, V. (Author), Vremera, T. (Author)
• Format: Article
• Language: English
• Published: MDPI 2022
• Subjects: booster dose; breakthrough infections; healthcare workers; host factors; immune response; SARS‐CoV‐2; vaccination
• Online Access: View Fulltext in Publisher

 The continuous variability of SARS‐CoV‐2 and the rapid waning of specific antibodies threatens the efficacy of COVID‐19 vaccines. We aimed to evaluate antibody kinetics one year after SARS‐CoV‐2 vaccination with an mRNA vaccine in healthcare workers (HCW), with or without a booster. A marked decline in anti‐Spike(S)/Receptor Binding Domain (RBD) antibody levels was registered during the first eight months post‐vaccination, followed by a transitory increase after the booster. At three months post‐booster an increased antibody level was maintained only in HCW vaccinated after a prior infection, who also developed a higher and long‐lasting level of anti‐S IgA antibodies. Still, IgG anti‐nucleocapsid (NCP) fades five months post‐SARS‐CoV‐2 infection. De-spite the decline in antibodies one‐year post‐vaccination, 68.2% of HCW preserved the neutraliza-tion capacity against the ancestral variant, with a decrease of only 17.08% in the neutralizing capacity against the Omicron variant. Nevertheless, breakthrough infections were present in 6.65% of all participants, without any correlation with the previous level of anti‐S/RBD IgG. Protection against the ancestral and Omicron variants is maintained at least three months after a booster in HCW, possibly reflecting a continuous antigenic stimulation in the professional setting. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.