Neonatal vitamin A supplementation and immune responses to oral polio vaccine in Zimbabwean infants

Background: Micronutrient deficiencies may contribute to reduced oral vaccine immunogenicity in developing countries. We hypothesised that neonatal vitamin A supplementation (NVAS) would improve oral vaccine responses.

Methods: We performed a cross-sectional study of infants recruited at birth to the Zimbabwe Vitamin A for Mothers and Babies (ZVITAMBO) trial, a randomised controlled trial of single, high-dose NVAS vs placebo conducted in Zimbabwe between 1997-2001. We measured poliovirus-specific IgA to type 1-3 polio strains by semiquantitative capture ELISA in cryopreserved plasma samples collected at 6 months of age.

Results: A total of 181 infants fulfilled inclusion criteria, of whom 80 were randomised to NVAS and 101 to placebo. There were no significant differences in baseline characteristics between groups. At 6 months of age, median (IQR) vaccine titres for infants randomised to NVAS vs placebo were 932 (421-3001) vs 1774 (711-5431) for Sabin-1 (p=0.04); 1361 (705-3402) vs 2309 (1081-4283) for Sabin-2 (p=0.15); and 1584 (796-4216) vs 2260 (996-5723) for Sabin-3 (p=0.14), respectively. After adjusting for breast feeding status, birth weight, season and infant sex in a linear regression model, there was only weak evidence of difference in log mean titres between vitamin A and placebo groups for Sabin-1 (p=0.08) and no evidence of difference in log mean titres for Sabin-2 and Sabin-3.

Conclusions: NVAS did not augment oral polio vaccine responses in Zimbabwean infants. Further research is required to understand the impact of NVAS on responses to other oral vaccines.The trial is registered with clinicaltrials.gov identifier: NCT00198718.