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Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Children and Adolescents: A Large-Scale Observational Study

23 Pages Posted: 15 Feb 2022

See all articles by Alejandro Jara

Alejandro Jara

Ministry of Health, Chile

Eduardo A. Undurraga

Pontificia Universidad Católica de Chile - Escuela de Gobierno

Juan Carlos Flores

Pontificia Universidad Católica de Chile - Faculty of Medicine

José R. Zubizarreta

Harvard University - Department of Health Care Policy

Cecilia Gonzalez

Ministry of Health, Chile

Alejandra Pizarro

Ministry of Health, Chile

Duniel Ortuño-Borroto

Ministry of Health, Chile

Johanna Acevedo

Ministry of Health, Chile

Katherinne Leo

Ministry of Health, Chile

Fabio Paredes

Ministry of Health, Chile

Tomas Bralic

Ministry of Health, Chile

Veronica Vergara

Ministry of Health, Chile

Francisco Leon

Ministry of Health, Chile

Ignacio Parot

Ministry of Health, Chile

Paulina Leighton

Ministry of Health, Chile

Pamela Suarez

Ministry of Health, Chile

Juan Carlos Rios

Ministry of Health, Chile

Heriberto E. Garcia-Escorza

Institute of Public Health of Chile; Ministry of Health, Chile

Rafael Araos

Ministry of Health, Chile; Facultad de Medicina Clínica Alemana Universidad del Desarrollo

More...

Abstract

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.

Methods: We used a large prospective national cohort of about two million children and adolescents 6 to 16 years to estimate the effectiveness of an inactivated SARS-CoV-2 vaccine (CoronaVac) in preventing Covid-19 cases, hospitalizations, and admission to intensive care unit (ICU). 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. 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 to 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, hospitalization, 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 hospitalization.

Interpretation: Our results suggest that a complete primary immunization schedule with the inactivated SARS-CoV-2 vaccine provides an effective protection against severe Covid-19 disease for children 6-16 years.

Funding Information: This research was supported by the Agencia Nacional de Investigación y Desarrollo (ANID) Millennium Science Initiative Program MIDAS [NCN17_059] to AJ; Advanced Center for Chronic Diseases (ACCDiS) ANID FONDAP [15130011] to RA; and Research Center for Integrated Disaster Risk Management (CIGIDEN) ANID FONDAP [15110017] to EU.

Declaration of Interests: The authors declare no conflicts of interest.

Ethics Approval Statement: The research protocol was approved by the Comité Ético Científico Clínica Alemana Universidad del Desarrollo. The study was considered exempt from informed consent, no human health risks were identified. Research analysts belong to the Chilean Ministry of Health; our use of data follows Chilean law 19.628 on personal data protection.

Keywords: SARS-CoV-2, Covid-19, vaccine effectiveness, inactivated SARS-CoV-2 vaccine, mRNA vaccine, pediatric cohort

Suggested Citation

Jara, Alejandro and Undurraga, Eduardo A. and Flores, Juan Carlos and Zubizarreta, José R. and Gonzalez, Cecilia and Pizarro, Alejandra and Ortuño-Borroto, Duniel and Acevedo, Johanna and Leo, Katherinne and Paredes, Fabio and Bralic, Tomas and Vergara, Veronica and Leon, Francisco and Parot, Ignacio and Leighton, Paulina and Suarez, Pamela and Rios, Juan Carlos and Garcia-Escorza, Heriberto E. and Araos, Rafael, Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Children and Adolescents: A Large-Scale Observational Study. Available at SSRN: https://ssrn.com/abstract=4035405 or http://dx.doi.org/10.2139/ssrn.4035405

Alejandro Jara

Ministry of Health, Chile

Santiago
Chile

Eduardo A. Undurraga

Pontificia Universidad Católica de Chile - Escuela de Gobierno ( email )

Chile

Juan Carlos Flores

Pontificia Universidad Católica de Chile - Faculty of Medicine ( email )

Chile

José R. Zubizarreta

Harvard University - Department of Health Care Policy ( email )

25 Shattuck Street
Boston, MA 02115
United States

Cecilia Gonzalez

Ministry of Health, Chile

Santiago
Chile

Alejandra Pizarro

Ministry of Health, Chile ( email )

Santiago
Chile

Duniel Ortuño-Borroto

Ministry of Health, Chile ( email )

Santiago
Chile

Johanna Acevedo

Ministry of Health, Chile

Santiago
Chile

Katherinne Leo

Ministry of Health, Chile ( email )

Santiago
Chile

Fabio Paredes

Ministry of Health, Chile

Santiago
Chile

Tomas Bralic

Ministry of Health, Chile

Santiago
Chile

Veronica Vergara

Ministry of Health, Chile

Santiago
Chile

Francisco Leon

Ministry of Health, Chile ( email )

Santiago
Chile

Ignacio Parot

Ministry of Health, Chile ( email )

Santiago
Chile

Paulina Leighton

Ministry of Health, Chile

Santiago
Chile

Pamela Suarez

Ministry of Health, Chile ( email )

Santiago
Chile

Juan Carlos Rios

Ministry of Health, Chile

Santiago
Chile

Heriberto E. Garcia-Escorza

Institute of Public Health of Chile ( email )

Chile

Ministry of Health, Chile ( email )

Santiago
Chile

Rafael Araos (Contact Author)

Ministry of Health, Chile ( email )

Santiago
Chile

Facultad de Medicina Clínica Alemana Universidad del Desarrollo ( email )

Santiago de Chile
Chile