Humoral and cellular response induced by a second booster of an inactivated SARS-CoV-2 vaccine in adults
Constanza Méndez, Hernán F. Peñaloza, Bárbara M. Schultz, Alejandro Piña-Iturbe, Mariana Ríos, Daniela Moreno‐Tapia, Patricia Pereira-Sánchez, Diane Leighton, Claudia Orellana, Consuelo Covarrubias, Nicolás M. S. Gálvez, Jorge A. Soto, Luisa F. Duarte, Daniela Rivera-Pérez, Yaneisi Vázquez, Alex Cabrera, Sergio Bustos, Carolina Iturriaga, Marcela Urzúa, María S Navarrete, Álvaro Rojas, Rodrigo Fasce, Jorge Onrubia Fernández, Judith Mora, Eugenio Ramı́rez, Aracelly Gaete-Argel, Mónica L. Acevedo, Fernando Valiente‐Echeverría, Ricardo Soto‐Rifo, Daniela Weiskopf, Alba Grifoni, Alessandro Sette, Gang Zeng, Weining Meng, Álvaro Rojas, María S Navarrete, Constanza Del Río, Dinely Del Pino, Natalia Aguirre, Grecia Salinas, Franco Vega, Acsa Salgado, Thomas Quinteros, Marlene Ortiz, Marcela Puente, Alma Muñoz, Patricio Astudillo, Nicole Le Corre, Marcela Potı́n, J.P. Catalán, Melan Peralta, Consuelo Zamanillo, Nicole Keller, Rocío Fernández, Sofía Aljaro, Sofía López, José Tomás González, Tania Weil, Luz Opazo, P. Rubio Muñoz, Inés Estay, Miguel Cantillana, Liliana Carrera, Matías Masalleras, Paula Guzmán, Francisca Aguirre, Aarón Cortés, Luis Federico Bátiz, Javiera Pérez, Karen Apablaza, L. D. Yates, María de los Ángeles Valdés, Bernardita Hurtado, Veronique Venteneul, Constanza Astorga, Paula Muñoz Venturelli, Pablo Vial, Andrea Schilling, Daniela Pavez, Inia Pérez, Amy Riviotta, Francisca González, Francisca Urrutia, Alejandra Del Río, Claudia Asenjo, Bárbara Vargas, Francisca Dias de Castro, Alejandra Acuña, Javiera Guzmán, Camila Astudillo, Carlos M. Pérez, Pilar Espinoza, Andrea Martínez, Marcela Arancibia, Harold V. Romero, Cecilia Bustamante, María Loreto Pérez, Natalia Uribe, Viviana Silva, Bernardita Morice
Abstract
Background The Omicron variant has challenged the control of the COVID-19 pandemic due to its immuno-evasive properties. The administration of a booster dose of a SARS-CoV-2 vaccine showed positive effects in the immunogenicity against SARS-CoV-2, effect that is even enhanced after the administration of a second booster. Methods During a phase-3 clinical trial, we evaluated the effect of a second booster of CoronaVac®, an inactivated vaccine administered 6 months after the first booster, in the neutralization of SARS-CoV-2 (n = 87). In parallel, cellular immunity (n = 45) was analyzed in stimulated peripheral mononuclear cells by flow cytometry and ELISPOT. Findings Although a 2.5-fold increase in neutralization of the ancestral SARS-CoV-2 was observed after the second booster when compared with prior its administration (Geometric mean units p < 0.0001; Geometric mean titer p = 0.0002), a poor neutralization against the Omicron variant was detected. Additionally, the activation of specific CD4 + T lymphocytes remained stable after the second booster and, importantly, equivalent activation of CD4 + T lymphocytes against the Omicron variant and the ancestral SARS-CoV-2 were found. Interpretation Although the neutralizing response against the Omicron variant after the second booster of CoronaVac® was slightly increased, these levels are far from those observed against the ancestral SARS-CoV-2 and could most likely fail to neutralize the virus. In contrast, a robust CD4 + T cell response may confer protection against the Omicron variant. Funding The Ministry of Health, Government of Chile, the Confederation of Production and Commerce, Chile and SINOVAC Biotech. NIH NIAID. The Millennium Institute on Immunology and Immunotherapy.