Long-term humoral and cellular immunity against vaccine strains and Omicron subvariants (BQ.1.1, BN.1, XBB.1, and EG.5) after bivalent COVID-19 vaccination

Front Immunol. 2024 May 2:15:1385135. doi: 10.3389/fimmu.2024.1385135. eCollection 2024.

Abstract

Background: The assessment of long-term humoral and cellular immunity post-vaccination is crucial for establishing an optimal vaccination strategy.

Methods: This prospective cohort study evaluated adults (≥18 years) who received a BA.4/5 bivalent vaccine. We measured the anti-receptor binding domain immunoglobulin G antibody and neutralizing antibodies (NAb) against wild-type and Omicron subvariants (BA.5, BQ.1.1, BN.1, XBB.1 and EG.5) up to 9 months post-vaccination. T-cell immune responses were measured before and 4 weeks after vaccination.

Results: A total of 108 (28 SARS-CoV-2-naïve and 80 previously infected) participants were enrolled. Anti-receptor binding domain immunoglobulin G (U/mL) levels were higher at 9 months post-vaccination than baseline in SAR-CoV-2-naïve individuals (8,339 vs. 1,834, p<0.001). NAb titers against BQ.1.1, BN.1, and XBB.1 were significantly higher at 9 months post-vaccination than baseline in both groups, whereas NAb against EG.5 was negligible at all time points. The T-cell immune response (median spot forming unit/106 cells) was highly cross-reactive at both baseline (wild-type/BA.5/XBB.1.5, 38.3/52.5/45.0 in SARS-CoV-2-naïve individuals; 51.6/54.9/54.9 in SARS-CoV-2-infected individuals) and 4 weeks post-vaccination, with insignificant boosting post-vaccination.

Conclusion: Remarkable cross-reactive neutralization was observed against BQ.1.1, BN.1, and XBB.1 up to 9 months after BA.4/5 bivalent vaccination, but not against EG.5. The T-cell immune response was highly cross-reactive.

Keywords: EG.5; SARS-CoV-2; cellular immunity; cross-reactivity; durability; humoral immunity; vaccines.

MeSH terms

  • Adult
  • Aged
  • Antibodies, Neutralizing* / blood
  • Antibodies, Neutralizing* / immunology
  • Antibodies, Viral* / blood
  • Antibodies, Viral* / immunology
  • COVID-19 Vaccines* / administration & dosage
  • COVID-19 Vaccines* / immunology
  • COVID-19* / immunology
  • COVID-19* / prevention & control
  • Female
  • Humans
  • Immunity, Cellular*
  • Immunity, Humoral*
  • Immunoglobulin G / blood
  • Immunoglobulin G / immunology
  • Male
  • Middle Aged
  • Prospective Studies
  • SARS-CoV-2* / immunology
  • T-Lymphocytes / immunology
  • Vaccination*

Supplementary concepts

  • SARS-CoV-2 variants

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study was supported by a grant from the Korea Disease Control and Prevention Agency (grant number: 2022ER260500).