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.

In this paper, the strengths and weaknesses of two Chilean political polls and the National Socioeconomic Characterisation Survey are analyzed from a statistical modelling point of view. The rationale of the analytical strategy is based on a distinction between identified parameters and parameters of interest. This is equivalent to make a distinction between what we can learn from the data provided by a survey and what we want to learn from those data. Using partial identification techniques, each survey is analyzed at di erent levels according to specific subpopulations. Based on these analyses, we emphasize not only the way in which the results should be reported, but also the necessity to make explicit the uncertainty induced by the non-response rates at the survey report.