Padoan A, Cosma C, Della Rocca F, Barbaro F, Santarossa C, Dall'Olmo L, Galla L, Cattelan A, Cianci V, Basso D, Plebani M. A cohort analysis of SARS-CoV-2 anti-spike protein receptor binding domain (RBD) IgG levels and neutralizing antibodies in fully vaccinated healthcare workers.
Clin Chem Lab Med 2022;
60:1110-1115. [PMID:
35473824 DOI:
10.1515/cclm-2022-0322]
[Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 04/13/2022] [Indexed: 01/01/2023]
Abstract
OBJECTIVES
The waning of humoral immunity after COVID-19 vaccine booster (third dose) has not yet been fully evaluated. This study updates data on anti-SARS-CoV-2 spike protein receptor binding domain (S-RBD) binding antibodies (bAb) and neutralizing antibodies (NAb) levels in individuals with homologous vaccination 3-4 months after receiving the booster dose.
METHODS
Fifty-five healthcare workers (HCW) from Padova University-Hospital were asked to collect serum samples for determining antibodies (Ab) at 12 (t12) and 28 (t28) days, at 6 months (t6m) after their first Comirnaty/BNT162b2 inoculation, and 3-4 months after receiving the 3rd homologous booster dose. HCW were monitored weekly for SARS-CoV-2 infection. Ab titers were measured by two chemiluminescent immunoassays, one targeting the S-RBD immunoglobulin G (IgG), and one surrogate viral neutralization test (sVNT), measuring NAb.
RESULTS
Twenty of the HCW had natural COVID-19 infection (COVID+) at different times, before either the first or the second vaccination. Median S-RBD IgG and NAb levels and their interquartile ranges 3-4 months after the 3rd dose were 1,076 (529-3,409) kBAU/L and 15.8 (11.3-38.3) mg/L, respectively, for COVID-, and 1,373 (700-1,373) kBAU/L and 21 (12.8-53.9) mg/L, respectively, for COVID+. At multivariate regression analyses, with age and gender included as covariates, S-RBD IgG bAb and sVNT NAb levels were closely associated with the time interval between serological determination and the 3rd vaccine dose (log10 _coeff=-0.013, p=0.012 and log10 _coeff=-0.010, p=0.025) for COVID+, whereas no such association was found in COVID- individuals.
CONCLUSIONS
The third booster dose increases anti-SARS-CoV-2 Ab levels, elevated levels persisting for up to 3-4 months. Waning of Ab levels appears to be less pronounced for COVID+ individuals.
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