Issues in selection of DTwP-based combination vaccines

This study examines regulatory, supply, acceptance and financing issues of combinations based on diphtheria-tetanus-pertussis (whole cell) vaccines (DTwP). These combination vaccines are currently produced in Europe mostly for export. Future regulatory oversight issues could have an impact on their availability. Before use of acellular pertussis-containing vaccines, the number of doses of DTwP vaccines offered in response to United Nations agency procurement tenders far exceeded the projected demand. Current demand and supply are converging. Most of that supply comes from developing country manufacturers, a potential new source of combination vaccines as well. The expected development and use of DTwP-based combination vaccines raises antigen allocation issues that could further affect supply. These combination vaccines have strong programmatic advantages, but pose complex selection issues involving disease burden, presentation, and availability of long-term financing. Vaccine price is not the major driving factor. A model examining important selection factors for regional country groupings provides predictions that have been validated by decisions on use of DTwP-based combination vaccines. This model may be useful in providing long-term uptake projections for other combination vaccines.