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Access type: UnknownAuthor: search.filters.author.Heriberto García-Escorza

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    Effectiveness of the second COVID-19 booster against Omicron: a large-scale cohort study in Chile
    (2023)
    Alejandro Jara
    ;
    Cristobal Cuadrado
    ;
    Eduardo A. Undurraga
    ;
    Christian García
    ;
    Manuel Nájera
    <jats:title>Abstract</jats:title><jats:p>In light of the ongoing COVID-19 pandemic and the emergence of new SARS-CoV-2 variants, understanding the effectiveness of various booster vaccination regimens is pivotal. In Chile, using a prospective national cohort of 3.75 million individuals aged 20 or older, we evaluate the effectiveness against COVID-19-related intensive care unit (ICU) admissions and death of mRNA-based second vaccine boosters for four different three-dose background regimes: BNT162b2 primary series followed by a homologous booster, and CoronaVac primary series followed by an mRNA booster, a homologous booster, and a ChAdOx-1 booster. We estimate the vaccine effectiveness weekly from February 14 to August 15, 2022, by determining hazard ratios of immunization over non-vaccination, accounting for relevant confounders. The overall adjusted effectiveness of a second mRNA booster shot is 88.2% (95%CI, 86.2–89.9) against ICU admissions and 90.5% (95%CI 89.4–91.4) against death. Vaccine effectiveness shows a mild decrease for all regimens and outcomes, probably linked to the introduction of BA.4 and BA.5 Omicron sub-lineages and the waning of immunity. Based on our findings, individuals might not need additional boosters for at least 6 months after receiving a second mRNA booster shot in this setting.</jats:p>
    Scopus© Citations 11  2
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    Effectiveness of an inactivated SARS-CoV-2 vaccine in children and adolescents: a large-scale observational study
    (2023)
    Alejandro Jara
    ;
    Eduardo A. Undurraga
    ;
    Juan Carlos Flores
    ;
    José R. Zubizarreta
    ;
    Cecilia González
      7Scopus© Citations 15
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    Effectiveness of homologous and heterologous booster doses for an inactivated SARS-CoV-2 vaccine: a large-scale prospective cohort study
    (2022)
    Alejandro Jara
    ;
    Eduardo A Undurraga
    ;
    José R Zubizarreta
    ;
    Cecilia González
    ;
    Alejandra Pizarro
      1Scopus© Citations 169
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    Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile
    (2021)
    Alejandro Jara
    ;
    Eduardo A. Undurraga
    ;
    Cecilia González
    ;
    Fabio Paredes
    ;
    Tomás Fontecilla
    Scopus© Citations 665  5
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    Effectiveness of CoronaVac in children 3–5 years of age during the SARS-CoV-2 Omicron outbreak in Chile
    (2022)
    Alejandro Jara
    ;
    Eduardo A. Undurraga
    ;
    José R. Zubizarreta
    ;
    Cecilia González
    ;
    Acevedo, Johanna
    <jats:title>Abstract</jats:title><jats:p>The outbreak of the B.1.1.529 lineage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Omicron) has caused an unprecedented number of Coronavirus Disease 2019 (COVID-19) cases, including pediatric hospital admissions. Policymakers urgently need evidence of vaccine effectiveness in children to balance the costs and benefits of vaccination campaigns, but, to date, the evidence is sparse. Leveraging a population-based cohort in Chile of 490,694 children aged 3–5 years, we estimated the effectiveness of administering a two-dose schedule, 28 days apart, of Sinovac’s inactivated SARS-CoV-2 vaccine (CoronaVac). We used inverse probability-weighted survival regression models to estimate hazard ratios of symptomatic COVID-19, hospitalization and admission to an intensive care unit (ICU) for children with complete immunization over non-vaccination, accounting for time-varying vaccination exposure and relevant confounders. The study was conducted between 6 December 2021 and 26 February 2022, during the Omicron outbreak in Chile. The estimated vaccine effectiveness was 38.2% (95% confidence interval (CI), 36.5–39.9) against symptomatic COVID-19, 64.6% (95% CI, 49.6–75.2) against hospitalization and 69.0% (95% CI, 18.6–88.2) against ICU admission. The effectiveness against symptomatic COVID-19 was modest; however, protection against severe disease was high. These results support vaccination of children aged 3–5 years to prevent severe illness and associated complications and highlight the importance of maintaining layered protections against SARS-CoV-2 infection.</jats:p>
    Scopus© Citations 82  8