Purpose: A translog cost function was estimated to investigate the cost impact of the expansion of vaccination clinics and the economical size of a mass vaccination clinic.

Methods: Due to limited opportunities to observe actual mass influenza vaccination clinics, we simulated data on the cost and number of persons vaccinated using parameters previously observed in pilot mass influenza vaccination clinics serving 2,000 people a day and wage statistics collected from the Census. The data simulation included an optimization procedure to minimize clinic program costs and patient waiting time, given parameters such as wage rates and input prices. Since the simulation replicates the clinics given fixed inputs such as space, tables and chairs, and patient flows, we used the simulated data and SAS/ETS to estimate a variable cost function of the translog functional form via Seemingly Unrelated Regressions (SUR). Cost flexibility is represented as the ratio of marginal cost to average cost (= MC/AC). With parameter estimates, cost flexibility and the number of patients at minimum average cost were computed using SAS/IML.

Results: 2,499 clinics were simulated. Cost flexibility was estimated to be 0.9682 and the number of patients for vaccination at minimum average cost was estimated approximately 6,109. Since MC = 0.9682×AC, we found that MC < AC. Thus, the average cost could be lowered by increasing the number of persons vaccinated at the minimum average cost up to 6,109 where MC=AC.

Conclusions: Our results show that it would be economical to invite more people (up to 6,109) to the current setting with the same amount of inputs instead of setting up new clinics. Of note is that the number of vaccinations at the minimum average cost greatly exceeds the original number of people targeted for vaccination at the pilot clinics. This implies that in the case of a public health emergency, when the value of patient waiting time would be of lesser consideration, large-scale mass vaccination clinics could serve many more patients than they originally targeted.