This work evaluated the immune response induced by two doses of CoronaVac separated by 4 weeks in healthy children and adolescents in Chile. To date, few studies have described the effects of CoronaVac in the pediatric population.

Background. Multiple vaccines against SARS-CoV-2 have been evaluated in clinical trials, but very few include the pediatric population. The inactivated vaccine CoronaVac® has shown to be safe and immunogenic in a phase 1/2 clinical trial in a pediatric cohort in China. This study is an interim safety and immunogenicity report of a phase 3 clinical trial for CoronaVac® in healthy children and adolescents in Chile. Methods. Participants aged 3 to 17 years old received two doses of CoronaVac® in a four-week interval. Local and systemic adverse reactions were registered in 699 participants that received the first dose and 381 that received the second dose until December 31st, 2021. Whole blood samples were collected from 148 participants for humoral and cellular immunity analyses. Results. The primary adverse reaction reported after the first and second dose was pain at the injection site. The adverse reactions observed were primarily mild and local, and no severe adverse events were reported. Four weeks after the second dose, a significant increase in the levels of total and neutralizing antibodies was observed. Increased activation of specific CD4+ T cells was also observed four weeks after the second dose. Although antibodies induced by vaccination neutralize variants Delta and Omicron, titers were lower than the D614G variant. Importantly, comparable T cell responses were detected against these variants of concern. Conclusions. CoronaVac® is safe and immunogenic in subjects aged 3-17 years old and is thus likely to confer protection against infection caused by SARS-CoV-2 variants in this target population.

MicroRNA-423 (miR-423) is highly expressed in breast cancer (BC). Previously, our group showed that the SNP rs6505162:C>A located in the pre-miR-423 was significantly associated with increased familial BC risk in patients with a strong family history of BC. Therefore, in this study, we evaluated the functional role of rs6505162 in mammary tumorigenesis in vitro to corroborate the association of this SNP with BC risk. We found that rs6505162:C>A upregulated expression of both mature miR-423 sequences (3p and 5p). Moreover, pre-miR-423-A enhanced proliferation, and promoted cisplatin resistance in BC cell lines. We also showed that pre-miR-423-A expression decreased cisplatin-induced apoptosis, and increased BC cell migration and invasion. We propose that the rs6505162-A allele promotes miR-423 overexpression, and that the rs6505162-A allele induces BC cell proliferation, viability, chemoresistance, migration, and invasion, and decreases cell apoptosis as a consequence. We suggest that rs6505162:C>A is a functional SNP site with potential utility as a marker for early diagnosis, prognosis, and treatment efficacy monitoring in BRCA1/2-negative BC patients, as well as a possible therapeutic target.

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