Rivera-Pérez, DanielaMéndez, ConstanzaDiethelm-Varela, BenjamínMelo-González, FelipeVázquez, YaneisiMeng, XingXin, QianqianFasce, Rodrigo A.Fernández, JorgeMora, JudithRamirez, EugenioAcevedo, Mónica L.Valiente-Echeverría, FernandoSoto-Rifo, RicardoGrifoni, AlbaWeiskopf, DanielaSette, AlessandroAstudillo, PatricioLe Corre, NicoleAbarca, KatiaPerret, CeciliaGonzález, Pablo A.Soto, Jorge A.Bueno, Susan M.Kalergis, Alexis M.2024-07-192024-07-192024Frontiers in Immunology Open Access Volume 152024 Article number 137219316643224https://repositorio.unab.cl/handle/ria/58607Indexación: Scopus.Background: Vaccine effectiveness against SARS-CoV-2 infection has been somewhat limited due to the widespread dissemination of the Omicron variant, its subvariants, and the immune response dynamics of the naturally infected with the virus. Methods: Twelve subjects between 3-17 years old (yo), vaccinated with two doses of CoronaVac®, were followed and diagnosed as breakthrough cases starting 14 days after receiving the second dose. Total IgGs against different SARS-CoV-2 proteins and the neutralizing capacity of these antibodies after infection were measured in plasma. The activation of CD4+ and CD8+ T cells was evaluated in peripheral blood mononuclear cells stimulated with peptides derived from the proteins from the wild-type (WT) virus and Omicron subvariants by flow cytometry, as well as different cytokines secretion by a Multiplex assay. Results: 2 to 8 weeks post-infection, compared to 4 weeks after 2nd dose of vaccine, there was a 146.5-fold increase in neutralizing antibody titers against Omicron and a 38.7-fold increase against WT SARS-CoV-2. Subjects showed an increase in total IgG levels against the S1, N, M, and NSP8 proteins of the WT virus. Activated CD4+ T cells showed a significant increase in response to the BA.2 subvariant (p<0.001). Finally, the secretion of IL-2 and IFN-γ cytokines showed a discreet decrease trend after infection in some subjects. Conclusion: SARS-CoV-2 infection in the pediatric population vaccinated with an inactivated SARS-CoV-2 vaccine produced an increase in neutralizing antibodies against Omicron and increased specific IgG antibodies for different SARS-CoV-2 proteins. CD4+ T cell activation was also increased, suggesting a conserved cellular response against the Omicron subvariants, whereas Th1-type cytokine secretion tended to decrease.enbreakthrough casesCoronaVac®inactivated SARS-CoV-2 vaccineomicron variantpediatricphase 3 clinical trialSARS-CoV-2ArtículoCC BY 4.0 ATTRIBUTION 4.0 INTERNATIONAL10.3389/fimmu.2024.1372193