Influenza Vaccine Efficacy in Tropical and Developing Countries

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A limited number of studies have suggested that influenza vaccination of select groups in a population provides protection to both vaccinated and unvaccinated persons, including those who respond poorly to vaccination, by decreasing transmission within a community to susceptible persons. Few studies have been conducted to assess the indirect effects of influenza vaccination, either at the household or the community level. Apart from an observational study that was conducted during the 1968 pandemic, few data are available to evaluate the effects of influenza vaccination on rates of illness among non-vaccinated persons in a community. Furthermore, no information is available on effectiveness of vaccines in populations from tropical, developing countries, where influenza vaccine use remains limited. In these countries, differences in social interactions, population density, household composition, and school attendance could alter the transmission characteristics of influenza compared to those in the United States and other developed countries in temperate climates. As the next influenza pandemic could arise in a tropical, developing country, such information is critical to effective planning and preparedness, but will also add to the general understanding of the dynamic interplay between influenza transmission, social structure, and population immunity. Information obtained from such studies will also provide important data on strategies for the use of influenza vaccine during a pandemic, when the supply of vaccine will likely be limited. Results from these studies will also provide important information on the epidemiology and disease burden of influenza in tropical regions, and on the potential benefits of seasonal vaccination programs in developing countries.

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