Antigen-specific T cell responses in SARS-CoV-2 mRNA-vaccinated children

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• SARS-CoV-2 mRNA vaccines induce comparable humoral immunity in children and adults.
• Early-life T cell responses to vaccination are not well understood and may differ from adult patterns.

Purpose of the Study:

• To investigate the nature and kinetics of T cell responses to mRNA vaccines in pediatric populations.
• To compare T cell immunity elicited by different mRNA vaccine doses in children.

Main Methods:

• Analysis of antigen-specific CD4+ T cell responses following BNT162b2 vaccination in adolescents (≥12 years).
• Comparison of T cell responses in younger children (5-11 years) with different vaccine doses (BNT162b2 vs. 100 μg mRNA1273).
• Assessment of T cell effector phenotypes and correlation with anti-receptor binding domain (RBD) antibody levels.

Main Results:

• BNT162b2 vaccination elicited significant antigen-specific CD4+ T cell responses in adolescents (≥12 years).
• The magnitude of T cell response was weaker in the 5- to 11-year-old cohort, and a higher dose of mRNA1273 did not improve this response.
• Younger children exhibited increased effector T cell phenotypes, correlating with higher anti-RBD antibody levels but reduced memory generation.

Conclusions:

• Pediatric T cell responses to mRNA vaccines are age-dependent, suggesting distinct developmental programming in early life.
• Age-specific adaptive immunity highlights the need to optimize vaccine priming conditions, including dose and potential adjuvants, for pediatric populations.