Objective: To assess the reactogenicity, measure the adaptive immune responses and track the long-term immune memory in 11-16-year-old young adolescents and their parents receiving the 3 COVID-19 vaccines-BNT162b2, CoronaVac and AZD1222-chosen by the Hong Kong Government; to compare the reactogenicity and immunogenicity across the 3 vaccines used for these children and their respective parents, and between the children and their parents.
Hypothesis: to be tested The safety profile and the magnitude and durability of immune responses to the 3 COVID-19 vaccines in young adolescents are non-inferior to those in middle-aged adults.
Design and subjects: A single-site, comparative nonrandomised clinical trial for 300 healthy individuals between 11-16 years old paired with one or both healthy parents to receive one of 3 COVID-19 vaccines-100 student-parent pairs for each vaccine.
Instruments: Mobile app for subjects to record adverse effects, enzyme-linked immunosorbent assay, plaque reduction neutralization assay, luciferase immunoprecipitation system assay and flow cytometry.
Interventions: BNT162b2, CoronaVac and AZD1222.
Main outcome measures: Types and frequencies of adverse effects within 7 days, and changes and peaks of antibody levels and antigen-specific memory T cell responses for 3 years.
Data analysis: Comparison of rates of each type of adverse effects, immune responses at each timepoint across the 3 vaccines and age groups by ANOVA and multivariate longitudinal statistical models, decay of immune response modelled by regression analysis.