ADDRESSING THE CHALLENGES TO IMMUNIZATION PRACTICE WITH AN ECONOMIC ALGORITHM FOR VACCINE SELECTION

The biotechnology revolution is producing a growing bounty of new vacc ines which pose difficult choices in selecting among many products. So me major public and private purchasers of vaccine may offer individual physicians and clinics their choice in assembling vaccine inventories . Others might purchase only a limited stock of products that would sa tisfactorily immunize a typical child. In either case, current vaccine selection decisions al-e based principally on purchase price alone wi thout systematic consideration of other factors of fiscal consequence. As a potential tool for decision making, we developed an economic alg orithm for vaccine selection that would minimize the overall costs of disease control through immunization by considering: (1) purchase pric e, (2) number of doses needed (3) preparation, time (4) route of admin istration, (5) cold storage needs, (6) shelf life, (7) earliest age of full immunity, (8) adverse events frequency, and (9) efficacy of prot ection. to demonstrate the algorithm, variables (I) to (4) above were incorporated into a pilot binary-integer linear programming model that satisfied the recommended immunization schedule for diphtheria, tetan us, pertussis, Haemophilus influenzae b, and hepatitis B, using eleven vaccines (DTaP, DTaP-Hib, Hib, HepB and Hib-HepB) from four manufactu rers. Five (or six) opportunities to vaccinate were modeled at (1), 2, 4, 6, 12-18, and 60 months of life, assuming US$40 per clinic visit, $15 per injection, and,$0.50 per minute of nurse preparation time. Vac cine costs were varied using actual March and September 1997 US Federa l vaccine prices, as well as estimates for unpriced new vaccines. Over 16000 distinct vaccine stocking lists by vaccine type and brand were possible. Including a I-month visit the lowest-cost 'solution' of the algorithm was $529.41 per child in the March cost-assumption case and $490.32 in the September one (both included four doses of DTaP-Hib, th ree HepB, and one DTaP). Without a 1-month visit, the lowest-cost solu tion in the Mar-ch case cost $486.67 (four DTaP, two Hib-HepB, one DTa P-Hib, and one HepB), while the September case cost $450.32 (four DTaP -Hib, three HepB, and one DTaP). Ensuring at least one product was sel ected from each of the four manufacturers increased costs about $13.00 , and the needed injections rose from eight to Mine. The most economic al selection of vaccines to use cannot be intuitively predicted, as pe rmutations are large and solutions are sensitive to minor changes in c osts and constraints. A transparent, objective selection method that w eighs the economic value of distinguishing features among competing va ccines might offer the 'best value' to vaccine pur chasers, while also creating strong market incentives for continuing innovation and compe tition in the vaccine industry. (C) 1998 Elsevier Science Ltd. All rig hts reserved.