A Tale of Two Responses: Vaccine vs. Natural Immunity in Young Atopic Children

ABSTRACT Aim To investigate baseline pneumococcal antibody levels and the influence of allergic sensitization in children under age six with recurrent respiratory infections. Methods We conducted a retrospective analysis of 38 fully immunised children (aged 2–5 years) with recurrent respiratory infections. Baseline serum pneumococcal antibody levels were measured against 23 serotypes. An adequate response was defined as protective levels (≥ 1.3 ug/mL) for at least 50% of tested serotypes. Associations between antibody levels and allergic sensitization (defined by skin prick test or specific IgE), asthma, and atopic dermatitis were evaluated. Results Inadequate baseline pneumococcal antibody levels were found in 71% of the cohort. Allergic sensitization was significantly associated with lower protective antibody levels for non‐conjugate serotypes (mean 26% vs. 51%, p = 0.04) but showed no significant correlation with conjugate vaccine serotypes. The prevalence of specific antibody deficiency was low at 5%. No significant associations were found between antibody levels and diagnosed asthma or atopic dermatitis. Conclusion Young children with recurrent respiratory infections frequently exhibit inadequate baseline immunity. Allergic sensitization is specifically linked to impaired responses to non‐conjugate polysaccharide antigens, suggesting atopy selectively hinders specific immune pathways.