Vaccine Effectiveness Among 5- to 17-year-old Individuals with Prior SARS-CoV-2 Infection: An EHR-Based Target Trial Emulation Study from the RECOVER Project

Area of Science:

• Pediatric Infectious Diseases
• Vaccinology
• Epidemiology

Background:

• The effectiveness of COVID-19 vaccines against SARS-CoV-2 reinfection in pediatric populations with prior infection is not well-established, especially concerning Omicron subvariants.
• Understanding vaccine effectiveness (VE) in this demographic is crucial for public health strategies.

Purpose of the Study:

• To evaluate the effectiveness of COVID-19 vaccination against SARS-CoV-2 reinfection in children and adolescents previously infected with the virus.
• To assess VE across different Omicron subvariant waves (BA.1/2, BA.4/5, XBB and later).

Main Methods:

• A retrospective cohort study using the RECOVER initiative's national electronic health record database.
• Emulation of target trials comparing previously SARS-CoV-2 infected individuals aged 5-17 years across different Omicron variant periods (January 2022 - August 2023).

Main Results:

• During the Omicron BA.1/2 period, VE against reinfection was 62% in children and 65% in adolescents.
• During the BA.4/5 period, VE was 57% in children, with no significant protection in adolescents.
• No statistically significant protection was observed for XBB or later subvariants in either age group.

Conclusions:

• COVID-19 vaccination demonstrated protection against reinfection in previously infected pediatric populations during the early and mid-Omicron waves.
• Vaccine effectiveness against reinfection decreased significantly with the emergence of later Omicron subvariants, highlighting the need for updated vaccine strategies.