The optimal number of routine vaccines to order at health clinics in low or middle income countries

Jayant Rajgopal, Diana L. Connor, Tina Marie Assi, Bryan A. Norman, Sheng I. Chen, Rachel R. Bailey, Adrienne R. Long, Angela R. Wateska, Kristina M. Bacon, Shawn T. Brown, Donald S. Burke, Bruce Y. Lee

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


In a low or middle income country, determining the correct number of routine vaccines to order at a health clinic can be difficult, especially given the variability in the number of patients arriving, minimal vaccination days and resource (e.g., information technology and refrigerator space) constraints. We developed a spreadsheet model to determine the potential impact of different ordering policies, basing orders on the arrival rates seen in the previous 1, 3, 6, or 12 sessions, or on long-term historical averages (where these might be available) along with various buffer stock levels (range: 5-50%). Experiments varied patient arrival rates (mean range: 1-30 per session), arrival rate distributions (Poisson, Normal, and Uniform) and vaccine vial sizes (range: 1-dose to 10-dose vials). It was found that when the number of doses per vial is small and the expected number of patients is low, the ordering policy has a more significant impact on the ability to meet demand. Using data from more prior sessions to determine arrival rates generally equates to a better ability to meet demand, although the marginal benefit is relatively small after more than 6 sessions are averaged. As expected, the addition of more buffer is helpful in obtaining better performance; however, this advantage also has notable diminishing returns. In general, the long-term demand rate, the vial sizes of the vaccines used and the method of determining the patient arrival rate all have an effect on the ability of a clinic to maximize the demand that is met.

Original languageEnglish
Pages (from-to)5512-5518
Number of pages7
Issue number33
StatePublished - Jul 26 2011


  • Logistics
  • Ordering
  • Vaccines


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