Causes of impaired oral vaccine efficacy in developing countries

Oral vaccines are less immunogenic when given to infants in low-income countries, compared with high-income countries, limiting their potential public health impact. In this review the authors evaluate the factors that might contribute to this phenomenon, including transplacental antibodies, breastfeeding, enteric pathogens and malnutrition, highlighting several clear risk factors for vaccine failure, such as the inhibitory effect of enteroviruses on oral poliovirus vaccine.

In addition, attention is brought to the ambiguous and at times contradictory nature of the available evidence on oral vaccines, 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.

“Deficits in the immunogenicity of oral vaccines targeting poliovirus, rotavirus and several other enteric pathogens have consistently been documented in settings where they might have the greatest benefit. Despite considerable effort, we are yet to fully determine the biological mechanisms responsible for this phenomenon, let alone how best to circumvent it.”

Read the full article in Future Microbiology.

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