Browsing by Author "Pizarro, Alejandra"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    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/).
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Effectiveness of CoronaVac in children 3-5 years of age during the SARS-CoV-2 Omicron outbreak in Chile
    (NATURE PORTFOLIO, 2022) Jara, Alejandro; Undurraga, Eduardo A.; Zubizarreta, Jose R.; Gonzalez, Cecilia; Acevedo, Johanna; Pizarro, Alejandra; Vergara, Veronica; Soto-Marchant, Mario; Gilabert, Rosario; Flores, Juan Carlos; Suarez, Pamela; Leighton, Paulina; Eguiguren, Pablo; Carlos Rios, Juan; Fernandez, Jorge; Garcia-Escorza, Heriberto; Araos, Rafael
    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.
  • Thumbnail Image
    Item
    Estrategia de pesquisa sistemática y seguimiento prolongado revela alto número de nuevas infecciones tuberculosas en contactos adultos en la Región Metropolitana, Chile
    (2020) Balcells Marty, María Elvira; Carvajal, Camila; Fernández, Paula; Ruiz-Tagle, Cinthya; Pizarro, Alejandra; García, Patricia; Peña, Carlos; Cuevas, Gerardo; Naves, Rodrigo
    Background: Contact investigation is cardinal in the control of tuberculosis (TB) since it helps to stop its transmission. In Chile, the National TB Program strategy does not include latent TB infection testing, regular chemoprophylaxis or follow-up in adults. Active TB was found in only 1.2% of contacts at country-level during 2018. Aim: To evaluate the performance of a systematic screening ofadult household contacts with targeted chemoprophylaxis and prolonged active follow-up. Material and Methods: Prospective cohort of household contacts in Santiago. Two face-to-face visits (at 0 and 12 weeks) that included QuantiFERON TB-Gold plus tests (QFT), chest radiography (CXR) at 0 and 24 weeks and, periodic text messaging or phone call follow-up for up to 48 weeks were implemented. Contacts with positive QFT were referred for TB chemoprophylaxis. Results: A total of 200 contacts were enrolled, 69% were migrants. At baseline evaluation, 45% had a positive QFT result and 1.6% had co-prevalent active TB. At follow-up, 13% contacts further converted to QFT (+), and 5.1% more were diagnosed with active TB (mean follow-up time 32 weeks). Of these 10 further active TB cases, 6 (60%) had a negative QFT and all (100%) had normal CXR at baseline; while three cases occurred in QFT converters. Conclusions: In this cohort of household contacts, 6.7 % were diagnosed with active TB (more than 2/3 at follow-up) and 13% had a late QFT (+) conversion. Active and prolonged contacts’ follow-up are essential to detect new infections and tackle the TB epidemic in Chile.