Primary Series and Booster Vaccine Effectiveness against COVID-19 Infection and Hospitalisation among 12 to 17-year-old Adolescents in Singapore

14 Pages Posted: 8 Jan 2022 Last revised: 15 Jun 2022

See all articles by Calvin J. Chiew

Calvin J. Chiew

National Centre for Infectious Diseases, Singapore; Ministry of Health, Singapore

Premikha M

Ministry of Health, Singapore

Chia Yin Chong

KK Women's and Children's Hospital

Wycliffe E. Wei

National Public Health and Epidemiology Unit, National Centre for Infectious Diseases

Benjamin Ong

Ministry of Health, Singapore

David Chien Lye

National Centre for Infectious Diseases

Derrick Heng

Ministry of Health, Singapore

Vernon J. Lee

Ministry of Health, Singapore

Kelvin Bryan Tan

Ministry of Health, Singapore

Date Written: June 15, 2022

Abstract

Background: Singapore offered the Pfizer-BioNTech/Comirnaty vaccine to adolescents aged 12 to 17 years old in May 2021, and extended booster vaccines to this group in January 2022. Literature on primary series and booster vaccine effectiveness among adolescents is limited outside of Europe and North America.

Methods: We studied the incidence of confirmed COVID-19 infection and hospitalisation among adolescents aged 12 to 17 years old vaccinated with Pfizer-BioNTech/Comirnaty in Singapore from 1 September to 15 December 2021 during the Delta-variant wave, and from 21 January to 28 April 2022 during the Omicron-variant wave.

Findings: Two doses of vaccination achieved vaccine effectiveness of 66% (95% CI 63% – 69%) against Delta-variant infection and 25% (95% CI 21% – 29%) against Omicron-variant infection, and 83% (95% CI 74% – 89%) against Delta-variant hospitalisation and 75% (95% CI 56% – 86%) against Omicron-variant hospitalisation. Booster vaccination with three doses achieved vaccine effectiveness of 56% (95% CI 53% – 58%) against Omicron-variant infection and 94% (95% CI 86% – 97%) against Omicron-variant hospitalisation, compared with unvaccinated adolescents. Vaccine effectiveness against infection after two doses waned over time, while vaccine effectiveness against hospitalisation remained stable; both were increased after three doses.

Interpretation: Among adolescents aged 12 to 17 years old, vaccine effectiveness against confirmed COVID-19 infection after two doses of Pfizer-BioNTech/Comirnaty decreased over time, and increased after a third dose. Boosted adolescents were also most protected from hospitalisation, compared with fully vaccinated, partially vaccinated and unvaccinated adolescents.

Note:
Funding: Funding: This study was not funded.

Declaration of Interests: The authors declare that they have no conflict of interest.

Ethics Approval Statement: This study was conducted as part of national COVID-19 public health response under the Infectious Disease Act, Ministry of Health, Singapore, with exemption from ethics review, as provided for under the Human Biomedical Research Act 2015, Singapore.

Keywords: COVID-19, SARS-CoV-2, vaccines, mRNA vaccine, adolescent, booster

Suggested Citation

Chiew, Calvin J. and M, Premikha and Chong, Chia Yin and Wei, Wycliffe E. and Ong, Benjamin and Lye, David Chien and Heng, Derrick and Lee, Vernon J. and Tan, Kelvin Bryan, Primary Series and Booster Vaccine Effectiveness against COVID-19 Infection and Hospitalisation among 12 to 17-year-old Adolescents in Singapore (June 15, 2022). Available at SSRN: https://ssrn.com/abstract=3996796 or http://dx.doi.org/10.2139/ssrn.3996796

Calvin J. Chiew (Contact Author)

National Centre for Infectious Diseases, Singapore

Singapore

Ministry of Health, Singapore ( email )

College of Medicine
16 College Road
Singapore, 169854
Singapore

Premikha M

Ministry of Health, Singapore ( email )

College of Medicine
16 College Road
Singapore, 169854
Singapore

Chia Yin Chong

KK Women's and Children's Hospital ( email )

Singapore

Wycliffe E. Wei

National Public Health and Epidemiology Unit, National Centre for Infectious Diseases ( email )

Benjamin Ong

Ministry of Health, Singapore ( email )

College of Medicine
16 College Road
Singapore, 169854
Singapore

David Chien Lye

National Centre for Infectious Diseases

Singapore

Derrick Heng

Ministry of Health, Singapore ( email )

College of Medicine
16 College Road
Singapore, 169854
Singapore

Vernon J. Lee

Ministry of Health, Singapore ( email )

College of Medicine
16 College Road
Singapore, 169854
Singapore

Kelvin Bryan Tan

Ministry of Health, Singapore ( email )

College of Medicine
16 College Road
Singapore, 169854
Singapore

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