Key result
Oral vaccine immunogenicity in infants in low-income countries is impaired by complex, interconnected factors including enteric pathogens, malnutrition, and microbiota dysbiosis.
Multiple interconnected factors, including enteric pathogens and malnutrition, contribute to the reduced immunogenicity of oral vaccines in developing countries, requiring tailored interventions.
Underscores need for integrated interventions to boost oral vaccine responses in low-income infants; leaves open dominant modifiable factors for targeted trials.
Oral vaccines are less immunogenic when given to infants in low-income compared with high-income countries, limiting their potential public health impact. Here, we review factors that might contribute to this phenomenon, including transplacental antibodies, breastfeeding, histo blood group antigens, enteric pathogens, malnutrition, microbiota dysbiosis and environmental enteropathy. We highlight several clear risk factors for vaccine failure, such as the inhibitory effect of enteroviruses on oral poliovirus vaccine. We also highlight the ambiguous and at times contradictory nature of the available evidence, which undoubtedly reflects the complex and interconnected nature of the factors involved. Mechanisms responsible for diminished immunogenicity may be specific to each oral vaccine. Interventions aiming to improve vaccine performance may need to reflect the diversity of these mechanisms.
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Parker et al. (2017) conducted a review in Impaired oral vaccine efficacy. Factors affecting oral vaccine efficacy (e.g., enteric pathogens, malnutrition, microbiota dysbiosis) was evaluated. Oral vaccine immunogenicity in infants in low-income countries is impaired by complex, interconnected factors including enteric pathogens, malnutrition, and microbiota dysbiosis.
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