Association between anaemia, micronutrient status, and pneumococcal vaccine responses in young Kenyan children

Anaemia and micronutrient deficiencies are common in low- and middle-income countries, but whether nutritional status influences pneumococcal vaccine immunogenicity in children remains poorly characterised. We examined associations between pneumococcal vaccine responses in 670 Kenyan children enrolled in three vaccine trials: PRISM (PCV10; n=195; NCT01028326 ), FPCV (fractional- and full-dose PCV10/PCV13; n=306; NCT03489018 ), and PATH-wSP (whole-cell pneumococcal vaccine; n=169; NCT02543892 ) and baseline anaemia and micronutrient status (iron, folate, zinc, and vitamins A, B12, D, and E). Analyses were performed separately for each trial. In the 1 mg PATH-wSP group, anaemia and iron deficiency anaemia were associated with lower composite IgG responses (adj. β −0.8 [−1.2, −0.4] and adj. β −0.7 [−1.2, −0.2], respectively). Higher vitamin B12 concentrations were associated with higher composite IgG (adj. β 0.4 [0.1, 0.7]) and opsonophagocytic activity (adj. β 0.4 [0.2, 0.7]) responses in the PRISM trial. There was little evidence of associations between biomarkers of iron status, folate, zinc, or vitamins A, D, and E and pneumococcal vaccine responses. These findings suggest that nutritional status is not a uniform determinant of pneumococcal vaccine immunogenicity, but that specific nutritional factors, particularly anaemia and vitamin B12 status, may influence vaccine responses in a context-dependent manner.