Abstract
Some vaccines show poor efficacy in tropical countries. Within a birth cohort in Uganda, we investigated factors that might influence responses to BCG and tetanus immunisation. Whole blood assay responses to crude culture filtrate proteins of Mycobacterium tuberculosis (cCFP)) and tetanus toxoid (TT) were examined among 1506 and 1433 one-year-olds, respectively. Maternal Mansonella perstans infection was associated with higher interleukin (IL)-10 responses to both immunogens but no reduction in gamma interferon (IFN-γ), IL-5 and IL-13 responses; other maternal helminth infections showed little effect. Tetanus immunisation during pregnancy was associated with higher infant responses to TT; maternal BCG scar (from past immunisation) with lower infant IL-5 and IL-13 responses to cCFP. IFN-γ, IL-5 and IL-13 to TT were reduced in HIV-exposed-uninfected infants; infant malaria and HIV were associated with lower IFN-γ, IL-5 and IL-13 responses to both immunogens. We conclude that maternal helminth infections are unlikely to explain poor vaccine efficacy in the tropics. Effects of maternal immunisation on infant responses to vaccines should be explored. Prevention of infant malaria and HIV could contribute to effectiveness of immunisation programmes.
Highlights
Immunisation is key to the control of infectious diseases but the efficacy of some vaccines is poor in tropical, developing countries, where they are most needed [1]
Tuberculosis remains a major cause of global morbidity and mortality [4]; effective immunisation could revolutionise tuberculosis control and new vaccines are being developed [5], but new vaccines may be influenced by the same factors that inhibit the response to BCG in the tropics
36 had not received BCG immunisation at Entebbe Hospital and 109 had incomplete tetanus immunisation: 1506 infants were included in analyses for responses following BCG immunisation, and 1433 for tetanus immunisation
Summary
Immunisation is key to the control of infectious diseases but the efficacy of some vaccines is poor in tropical, developing countries, where they are most needed [1]. Calmette-Guérin (BCG) immunisation has over 70% efficacy against tuberculosis in temperate countries, but low efficacy in tropical settings [2,3] The reasons for this need to be understood. Tuberculosis remains a major cause of global morbidity and mortality [4]; effective immunisation could revolutionise tuberculosis control and new vaccines are being developed [5], but new vaccines may be influenced by the same factors that inhibit the response to BCG in the tropics. Understanding these factors may allow the development of interventions to improve the effectiveness of immunisation programmes.
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