Browsing by Author "Vergara, Verónica"

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    Effectiveness and duration of a second COVID-19 vaccine booster
    (2022) Jara, Alejandro; Cuadrado, Cristobal; Undurraga Fourcade, Eduardo Andrés; García, Christian; Najera, Manuel; Bertoglia, María Paz; Vergara, Verónica; Fernández, Jorge; García, Heriberto; Araos, Rafael
    Using a prospective national cohort of 3.75 million individuals aged 20 or older, we evaluated the effectiveness against COVID-19 related ICU admissions and death of mRNA-based second vaccine boosters for four different three-dose background regimes: BNT162b2 primary series plus a homologous booster, and CoronaVac primary series plus an mRNA booster, a homologous booster, and a ChAdOx-1 booster. We estimated the vaccine effectiveness weekly from February 14 to August 15, 2022, by estimating hazard ratios of immunization over non-vaccination, accounting for relevant confounders. The overall adjusted effectiveness of a second mRNA booster shot was 88.2% (95%CI, 86.2-89.9) and 90.5% (95%CI 89.4-91.4) against ICU admissions and death, respectively. Vaccine effectiveness showed a mild decrease for all regimens and outcomes, probably associated with the introduction of BA.4 and BA.5 Omicron sub-lineages and immunity waning. The duration of effectiveness suggests that no additional boosters are needed six months following a second booster shot.
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    Effectiveness of the second COVID-19 booster against Omicron: a large-scale cohort study in Chile
    (2023) Jara Vallejos, Alejandro Antonio; Cuadrado, Cristóbal; Undurraga Fourcade, Eduardo Andrés; García, Christian; Nájera, Manuel; Bertoglia, María Paz; Vergara, Verónica; Fernández, Jorge; García-Escorza, Heriberto; Araos, Rafael
    In light of the ongoing COVID-19 pandemic and the emergence of new SARSCoV-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 nonvaccination, 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 ofimmunity. 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.