Pediatric Vaccination Efficacy Against SARS-CoV-2 Variants

Vaccination of children and adolescents against SARS-CoV-2 has markedly reduced severe disease and hospitalisation, yet the emergence of successive variants has challenged immunological protection. mRNA and inactivated vaccines elicit robust antibody and cellular responses in young populations, though neutralising titres against highly divergent strains such as Omicron are often attenuated. Real-world effectiveness studies demonstrate high initial protection against symptomatic infection with earlier variants, with gradual waning over weeks to months, while protection against severe outcomes remains comparatively durable. Immunological imprinting from prior infection or vaccination shapes subsequent variant responses, with ancestral-focused memory potentially limiting breadth of neutralisation. Booster strategies, variant-adapted formulations and heterologous schedules are under investigation to optimise cross-variant immunity in paediatric cohorts. Equitable vaccine deployment and continued surveillance are essential to safeguard children globally and to sustain in-person education and social development.

Research from Nature Portfolio

Recent studies have characterised how primary Omicron infection in children induces weak neutralising antibody responses, whereas subsequent reinfection or COVID-19 vaccination broadens neutralisation across Omicron sublineages and earlier variants. Despite this, the initial antibody repertoire remains largely focused on ancestral spike, illustrating immunological imprinting. Cellular immunity, by contrast, is uniformly robust across age groups and variants, offering protection against severe disease regardless of humoral breadth.

Evidence from a large cohort of 3–5-year-olds during an Omicron-dominated outbreak shows that two doses of inactivated vaccine confer modest protection against symptomatic illness (~38 %) but strong protection against hospital admission (~65 %) and ICU admission (~69 %). These findings support inclusion of young children in vaccination programmes to avert severe outcomes.

Comparative immunogenicity assessments in adolescents reveal that two doses of mRNA vaccine elicit higher spike-specific neutralising antibody titres, greater avidity and enhanced Fc-receptor binding than two doses of inactivated vaccine. Both platforms induce potent T cell responses; however, inactivated vaccine uniquely generates nucleocapsid-specific cellular immunity, which may influence long-term durability and cross-variant protection.

Pediatric Vaccination Efficacy Against SARS-CoV-2 Variants publication trend

The graph below shows the total number of articles in pediatric vaccination efficacy against sars-cov-2 variants across all publications each year (not limited to Nature Index journals).

Technical terms

Neutralising antibodies: Antibodies capable of blocking viral entry into host cells, thereby preventing infection.

Test-negative design: An observational study method comparing vaccination rates between symptomatic individuals who test positive and those who test negative for the pathogen.

Immunological imprinting: The tendency of the immune system to preferentially recall responses to the first encountered antigen, affecting responses to related variants.

Variant of concern (VOC): A viral lineage with mutations that enhance transmissibility, immune escape, or disease severity.

References

1. Immunological imprinting of humoral immunity to SARS-CoV-2 in children. Nature Communications (2023).
2. Effectiveness of CoronaVac in children 3–5 years of age during the SARS-CoV-2 Omicron outbreak in Chile. Nature Medicine (2022).
3. Immunogenicity and reactogenicity of SARS-CoV-2 vaccines BNT162b2 and CoronaVac in healthy adolescents. Nature Communications (2022).
4. Vaccine effectiveness of two-dose BNT162b2 against symptomatic and severe COVID-19 among adolescents in Brazil and Scotland over time: a test-negative case-control study. The Lancet Infectious Diseases (2022).
5. Omicron variant susceptibility to neutralizing antibodies induced in children by natural SARS-CoV-2 infection or COVID-19 vaccine. Emerging Microbes & Infections (2022).
6. Early Release - Effectiveness of BNT162b2 Vaccine in Adolescents during Outbreak of SARS-CoV-2 Delta Variant Infection, Israel, 2021 - Volume 27, Number 11—November 2021 - Emerging Infectious Diseases journal - CDC. Emerging Infectious Diseases (2021).