Background: Maternally HIV-exposed (mHIV-EU) infants have poor health even without HIV-1 infection. The responses to vaccination are less well defined. Immunity to oral Poliovirus vaccine (OPV) was studied in Zambian infants participating in a randomised controlled trial of micronutrient fortification to improve child health. Method: Maternally HIV-unexposed and mHIV-EU infants were recruited at 6 months age and randomised to basal or enriched micronutrient-fortified diets for 12 months. HIV-exposed mother-infant pairs had received perinatal nevirapine to prevent mother-to-child-transmission. In the cohort of 597 infants, neutralising-antibody titres to OPV were analysed at 18 months with respect to micronutrient fortification, maternal or infant HIV-1 infection, and human cytomegalovirus (HCMV) infection detected by antibodies and viremia (serum DNA).Vaccine protection was defined as log 2 titre>3. Results: Compared to uninfected children, HIV-1-infected children had reduced neutralising antibody titres to OPV, irrespective of diet: log 2 titre difference (95% confidence interval) -3.44(-2.41;-4.46) p<0.01. OPV antibody titres were lower in HIV-infected children with HCMV viremia compared to those without viremia at 18 months, but did not reach significance: difference -2.55(-6.10;1.01) p=0.14.Breastfeeding duration was independently associated with increasing OPV titre (pvalue<0.01). In mHIV-EU children there were reduced neutralising antibody titres to poliovirus compared with maternally HIV-unexposed, irrespective of diet, maternal education and socioeconomic status: log 2 titre difference (95% confidence interval) -0.56 (-0.98; -0.15) p<0.01. This difference was noticeably decreased after adjusting for breast-feeding duration, suggesting that in our study population less breast-feeding by HIV-positive mothers could explain the reduced OPV titres in mHIV-EU infants. Conclusion: The mHIV-EU infants had reduced polio vaccine antibody titres which were associated with reduced breast-feeding duration. This has important implications for polio eradication and control of vaccine-2 preventable diseases, in countries where childhood HIV-1 infection and maternal exposure are public health threats.
Highlights• Both maternally HIV-exposed and infected infants had reduced neutralisingantibodies to polio vaccine • The proportion of antibody-titres below protective levels were increased in both maternally HIV-exposed and infected infants.• Trial of micronutrient fortification in 743 randomised infants had no effect on vaccine antibody titre • We report effects of breast-feeding and HCMV infection on reduced antibody titres 3