Risk-based Vaccines and the Need for Risk-based Subnational Vaccination Strategies for Introduction

Most vaccines in the Expanded Program on Immunization are universal childhood vaccines (eg, measles and rotavirus vaccines). Other vaccines such as typhoid conjugate (TCV) and Japanese encephalitis vaccines are risk based and only used in countries where populations are at risk of these diseases. However, strategies to introduce risk-based vaccines are becoming complex due to increasing intracountry variability in disease incidence. There is a need to assess whether subnational vaccine strategies are appropriate.

Subnational strategies consider intracountry heterogeneous risk and prioritize vaccination only in those areas that are at risk; there is no intent to introduce the vaccine nationally. The following variables should be considered to determine appropriateness of subnational strategies: disease burden, outbreak potential, treatment availability and costs, cost-effectiveness, and availability of other preventive interventions. We propose criteria for each variable and use a hypothetical country considering TCV introduction to show how criteria are applied to determine if a subnational strategy is appropriate. Challenges include granularity of disease-burden data, political challenges of vaccinating only a portion of a population, and potentially higher costs of introduction. Benefits include targeted reduction of disease burden, increased equity for marginalized populations, and progress on development goals.

In the absence of perfect information at the national level, adopting a subnational vaccine strategy can provide country decision makers with an alternative to national vaccine introduction. Given the changing nature of communicable disease burden, subnational vaccination may be a tool to effectively avert mortality and morbidity while maximizing the use of available health and financial resources.