Abstract
Despite high vaccination coverage and considerable progress in reducing cases and deaths from diphtheria, tetanus, and pertussis, these diseases remain endemic in many countries. The World Health Organization recommends three booster doses of diphtheria- tetanus- pertussis-containing vaccines (DTPCV) to extend protection against these diseases into adulthood. An early childhood booster is recommended at 12–23 months, a childhood booster at 4–7 years, and an adolescent booster at 9–15 years of age. To provide and sustain optimal pertussis, tetanus and diphtheria immunity for both sexes, age- and epidemiologically appropriate combinations of DTPCVs should be used. As these booster doses are administered at ages beyond the primary vaccination series recommended in the first year of life, they require additional vaccination encounters and potentially different delivery platforms (e.g., school-based) that may incur delivery costs that differ from costs incurred to deliver the primary series. To support country-level decision-making, there is a need for evidence regarding the potential health and cost impacts of introducing these booster doses.
DTP Boost is a new interactive web-based tool developed by the Modelling and Simulation Hub, Africa (MASHA) at the University of Cape Town in collaboration with AFENET and U.S. CDC with guidance from an expert steering committee. The tool allows users to design vaccination strategies to explore the health impact, budget impact, and cost-effectiveness of introducing DTPCV booster doses in a selected country, focusing primarily on use for low- and middle-income country settings that have not yet introduced DTPCV boosters. Multiple vaccination strategies can be designed, allowing a detailed and interactive exploration of the relative costs and benefits of different numbers of DTPCV booster doses, vaccination coverage levels, introduction approaches (e.g., concurrent, staggered), vaccine formulations and vaccination delivery platforms (e.g., health facility, outreach site, school-based).
DTP Boost is powered by an integrated epidemiological and health economic model. Because diphtheria, pertussis and tetanus have fundamentally different disease processes, three semi-independent deterministic age-structured compartmental models have been developed. These three models are linked through vaccination and population dynamics. The models are tailored to the selected country, accounting for differences in existing vaccination schedule, current burden of disease, health systems characteristics, costs of illness and vaccination. The integrated health economic model uses the outputs from each disease model (e.g., numbers of clinical cases, deaths), cases per treatment setting (e.g., outpatient, inpatient), and number of doses of vaccine administered to compute benefits (e.g., cases and deaths averted) and costs (e.g., the financial and economic costs of routine vaccination, new vaccine introduction and costs of illness) for further health economic analysis. A budget impact analysis and separate cost-effectiveness analysis are presented for each vaccination strategy designed by the user. Results are reported in local currency for the selected country as well as US dollars for comparison. The health economic analyses are carried out from the provider perspective.
We will demonstrate the DTP Boost tool then discuss the results and lessons learned from its design and first use.