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Background <p>The Omicron lineage of SARS-CoV-2 showed a remarkable ability to escape vaccine-induced immunity. In a Phase 2 clinical trial, we investigated whether a third booster/fifth dose of one of three inactivated SARS-CoV-2 vaccine candidates, based on the Delta and Omicron BA.1 variants, enhanced humoral and cellular immune responses against SARS-CoV-2.</p> Methods <p>Volunteers who received either four doses of CoronaVac® (homologous group, <i>n</i> = 228) or two doses of CoronaVac® followed by two mRNA vaccine doses (heterologous group, <i>n</i> = 298) were randomly assigned to receive an Omicron BA.1-based, trivalent (ancestral, Delta, Omicron BA.1) inactivated vaccine or an additional dose of CoronaVac® (heterologous group only). Local and systemic adverse events were recorded for 7&#xa0;days after immunization with the fifth dose. Blood samples were collected at the time of immunization (day 0), 28&#xa0;days post-immunization, and 180&#xa0;days post-immunization. The immune response induced by vaccination was evaluated by quantifying total IgG against SARS-CoV-2 and neutralizing antibodies, IgG-producing B cells, relative antibody avidity, SARS-CoV-2-specific CD4<sup>+</sup> and CD8<sup>+</sup> T cells, and IFN-γ-producing cells.</p> Results <p>The most common local adverse event was pain at the site of inoculation (deltoid area), reported in 43.2% of the participants. No severe adverse events related to vaccination were recorded. Increased SARS-CoV-2-specific IgGs were observed exclusively in the homologous group at 28&#xa0;days post-vaccination compared to the pre-immune status. Reduced neutralizing antibodies against the Omicron BA.1 variant were detected in both groups when compared to the ancestral (WT) virus, and no changes in IgG-producing B cells or relative antibody avidity were observed after vaccination. Furthermore, we observed sustained IFN-γ production and the frequency of SARS-CoV-2-specific CD4<sup>+</sup> and CD8<sup>+</sup> T cells before and after vaccination.</p> Conclusions <p>Previous immunizations targeting the WT SARS-CoV-2 virus have induced a robust humoral and cellular response in the population, which is sustained by a fifth dose targeting either the Omicron BA.1, Delta, or WT virus.</p> Trial registration <p>No. NCT05593042.</p>

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A booster dose of an inactivated SARS-CoV-2 vaccine targeting virus variants sustains protective humoral and cellular immunity

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月15日

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  • Constanza Méndez,
  • Linmar Rodríguez-Guilarte,
  • Pablo A. Palacios,
  • Cristian Gutierrez-Vera,
  • Francisca Román,
  • Daniela Moreno-Tapia,
  • Mariana Ríos,
  • Antonia Reyes,
  • Felipe A. Cancino,
  • Francisco F. Otero,
  • Constanza Zurita,
  • Daniela Rivera,
  • Alex Cabrera,
  • Luisa F. Duarte,
  • Marcela Urzúa,
  • Carolina Iturriaga,
  • Álvaro Rojas,
  • Carlos M. Perez,
  • Andrea Schilling Redlich,
  • Rodrigo A. Fasce,
  • Jorge Fernández,
  • Judith Mora,
  • Eugenio Ramírez,
  • Angélica Domínguez,
  • Daniela Weiskopf,
  • Alba Grifoni,
  • Alessandro Sette,
  • Gang Zeng,
  • Weining Meng,
  • David Goldbatt,
  • Marina Johnson,
  • José V. González-Aramundiz,
  • María J. Álvarez-Figueroa,
  • Katia Abarca,
  • Leandro J. Carreño,
  • Pablo A. González,
  • Alexis M. Kalergis,
  • Hernán F. Peñaloza,
  • Susan M. Bueno

摘要

Background

The Omicron lineage of SARS-CoV-2 showed a remarkable ability to escape vaccine-induced immunity. In a Phase 2 clinical trial, we investigated whether a third booster/fifth dose of one of three inactivated SARS-CoV-2 vaccine candidates, based on the Delta and Omicron BA.1 variants, enhanced humoral and cellular immune responses against SARS-CoV-2.

Methods

Volunteers who received either four doses of CoronaVac® (homologous group, n = 228) or two doses of CoronaVac® followed by two mRNA vaccine doses (heterologous group, n = 298) were randomly assigned to receive an Omicron BA.1-based, trivalent (ancestral, Delta, Omicron BA.1) inactivated vaccine or an additional dose of CoronaVac® (heterologous group only). Local and systemic adverse events were recorded for 7 days after immunization with the fifth dose. Blood samples were collected at the time of immunization (day 0), 28 days post-immunization, and 180 days post-immunization. The immune response induced by vaccination was evaluated by quantifying total IgG against SARS-CoV-2 and neutralizing antibodies, IgG-producing B cells, relative antibody avidity, SARS-CoV-2-specific CD4+ and CD8+ T cells, and IFN-γ-producing cells.

Results

The most common local adverse event was pain at the site of inoculation (deltoid area), reported in 43.2% of the participants. No severe adverse events related to vaccination were recorded. Increased SARS-CoV-2-specific IgGs were observed exclusively in the homologous group at 28 days post-vaccination compared to the pre-immune status. Reduced neutralizing antibodies against the Omicron BA.1 variant were detected in both groups when compared to the ancestral (WT) virus, and no changes in IgG-producing B cells or relative antibody avidity were observed after vaccination. Furthermore, we observed sustained IFN-γ production and the frequency of SARS-CoV-2-specific CD4+ and CD8+ T cells before and after vaccination.

Conclusions

Previous immunizations targeting the WT SARS-CoV-2 virus have induced a robust humoral and cellular response in the population, which is sustained by a fifth dose targeting either the Omicron BA.1, Delta, or WT virus.

Trial registration

No. NCT05593042.