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Humoral and cellular response induced by a second booster of an inactivated SARS-CoV-2 vaccine in adults

Melo-Gonzalez, F.; Mendez, C.; Penaloza, H. F.; Schultz, B. M.; Pina-Iturbe, A.; Rios, M.; Moreno-Tapia, D.; Pereira-Sanchez, P.; Leighton, D.; Orellana, C.; Covarrubias, C.; Galvez, N. M.; Soto, J. A.; DUARTE, L. F.; Rivera-Perez, D.; Vazquez, Y.; Cabrera, A.; Bustos, S.; Iturriaga, C.; Urzua, M.; Navarrete, M. S.; Rojas, A.; Fasce, R.; Fernandez, J.; Mora, J.; Ramirez, E.; Gaete-Argel, A.; Acevedo, M.; Valiente-Echeverria, F.; Soto-Rifo, R.; Weiskopf, D.; Grifoni, A.; Sette, A.; Zeng, G.; Meng, W.; CoronaVac03CL Study Group, ; Gonzalez-Aramundiz, J. V.; Gonzalez, P. A.; Abarca, K.; Bueno, S

2022-08-23 infectious diseases
10.1101/2022.08.22.22279080 medRxiv
Show abstract

The SARS-CoV-2 Omicron variant has challenged the control of the COVID-19 pandemic even in highly vaccinated countries. While a second booster of mRNA vaccines improved the immunity against SARS-CoV-2, the humoral and cellular responses induced by a second booster of an inactivated SARS-CoV-2 vaccine have not been studied. In the context of a phase 3 clinical study, we report that a second booster of CoronaVac(R) increased the neutralizing response against the ancestral virus yet showed poor neutralization against the Omicron variant. Additionally, isolated PBMCs displayed equivalent activation of specific CD4+ T cells and IFN-{gamma} production when stimulated with a mega-pool of peptides derived from the spike protein of the ancestral virus or the Omicron variant. In conclusion, a second booster dose of CoronaVac(R) does not improve the neutralizing response against the Omicron variant compared with the first booster dose, yet it helps maintaining a robust spike-specific CD4+ T cell response.

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