Browsing by Author "Leon, Francisco"

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    Effectiveness of an inactivated SARS-CoV-2 vaccine in children and adolescents: a large-scale observational study
    (ELSEVIER, 2023) Jara, Alejandro; Undurraga, Eduardo A.; Flores, Juan Carlos; Zubizarreta, Jose R.; Gonzalez, Cecilia; Pizarro, Alejandra; Ortuno-Borroto, Duniel; Acevedo, Johanna; Leo, Katherinne; Paredes, Fabio; Bralic, Tomas; Vergara, Veronica; Leon, Francisco; Parot, Ignacio; Leighton, Paulina; Suarez, Pamela; Rios, Juan Carlos; Garcia-Escorza, Heriberto; Araos, Rafael
    Background Policymakers urgently need evidence to adequately balance the costs and benefits of mass vaccination against COVID-19 across all age groups, including children and adolescents. In this study, we aim to assess the effectiveness of CoronaVac's primary series among children and adolescents in Chile. Methods We used a large prospective national cohort of about two million children and adolescents 6-16 years to estimate the effectiveness of an inactivated SARS-CoV-2 vaccine (CoronaVac) in preventing laboratory-confirmed symptomatic SARS-CoV-2 infection (COVID-19), hospitalisation, and admission to an intensive care unit (ICU) associated with COVID-19. We compared the risk of individuals treated with a complete primary immunization schedule (two doses, 28 days apart) with the risk of unvaccinated individuals during the follow-up period. The study was conducted in Chile from June 27, 2021, to January 12, 2022, when the SARS-CoV-2 Delta variant was predominant but other variants of concern were co-circulating, including Omicron. We used inverse probability-weighted survival regression models to estimate hazard ratios of complete immunization over the unvaccinated status, accounting for time-varying vaccination exposure and adjusting for relevant demographic, socioeconomic, and clinical confounders.Findings The estimated adjusted vaccine effectiveness for the inactivated SARS-CoV-2 vaccine in children aged 6-16 years was 74.5% (95% CI, 73.8-75.2), 91.0% (95% CI, 87.8-93.4), 93.8% (95% CI, 87.8-93.4) for the prevention of COVID-19, hospitalisation, and ICU admission, respectively. For the subgroup of children 6-11 years, the vaccine effectiveness was 75.8% (95% CI, 74.7-76.8) for the prevention of COVID-19 and 77.9% (95% CI, 61.5-87.3) for the prevention of hospitalisation.Interpretation Our results suggest that a complete primary immunization schedule with the inactivated SARS-CoV-2 vaccine provides effective protection against severe COVID-19 disease for children 6-16 years.Copyright & COPY; 2023 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
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    Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile
    (MASSACHUSETTS MEDICAL SOC, 2021) Jara, Alejandro; Undurraga, Eduardo A.; Gonzalez, Cecilia; Paredes, Fabio; Fontecilla, Tomas; Jara, Gonzalo; Pizarro, Alejandra; Acevedo, Johanna; Leo, Katherine; Leon, Francisco; Sans, Carlos; Leighton, Paulina; Suarez, Pamela; Garcia Escorza, Heriberto; Araos, Rafael
    Inactivated SARS-CoV-2 Vaccine in Chile In a national prospective cohort study involving 10.2 million participants in Chile, the effectiveness of an inactivated SARS-CoV-2 vaccine, which had been developed in China and administered in two doses 28 days apart, was estimated. Effectiveness among fully immunized persons was estimated at 65.9% for Covid-19 and at 87.5% for hospitalization, 90.3% for ICU admission, and 86.3% for death.