MOTHERS’ WILLINGNESS TO PAY FOR CHILDHOOD VACCINATION IN TANZANIA: EVIDENCE FROM A TWO-PART INTERVAL REGRESSION MODEL WITH EQUITY IMPLICATION
Author(s)
Sarata NGACK, BSc, MPH, RN1, Jan Ostermann, PhD2, Ibitein Ngowari Okeafor, MPH3, Salome-Joelle Gass, MPH2, Mojtaba Kazemian, MPH4.
1Health Services Policy and Management, University of South Carolina, West Columbia, SC, USA, 2Health Services Policy and Management, University of South Carolina, Columbia, SC, USA, 3Health Services Policy and Management, University of South Carolina, COLUMBIA, SC, USA, 4Health Services Policy and Management, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
1Health Services Policy and Management, University of South Carolina, West Columbia, SC, USA, 2Health Services Policy and Management, University of South Carolina, Columbia, SC, USA, 3Health Services Policy and Management, University of South Carolina, COLUMBIA, SC, USA, 4Health Services Policy and Management, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
OBJECTIVES: This study elicited mothers’ willingness to pay (WTP) for routine childhood vaccination in Tanzania using double-bounded contingent valuation methods. WTP was analyzed using a two-part interval-censored regression model that accommodated left- and interval censoring and skewness in WTP data, while producing equity-relevant welfare measures.
METHODS: A cross-sectional cluster sample survey of 400 mothers from 4 rural districts in Tanzania was conducted from June-July 2024. Mothers were asked how much they would be willing to pay for each vaccination if they were no longer freely available. Using a two-part interval regression approach, we estimated the probability of strictly positive WTP (stage one) and the magnitude of WTP among payers (stage two). Conditional (among WTP-positive) and unconditional (population) mean WTP were estimated using parametric log-normal retransformations with Duan’s smearing correction and bootstrapped standard errors. Equity analysis involved comparisons of conditional and unconditional mean WTP across wealth quintiles.
RESULTS: Approximately 85% of respondents indicated a positive WTP. The conditional mean WTP among WTP-positive mothers was TSH 3608 (USD 1.34) (95% CI TSH 3107 - 4510) after applying Duan’s smearing correction (1 USD = 2685 TSH). Unconditional population-average WTP, accounting for zero WTP among a subset of mothers, was substantially lower: TSH 3237 (USD 1.21) (95% CI TSH 2536 - 3837). Both the probability of positive WTP and the unconditional WTP increased monotonically with wealth quintile, reflecting a pro-rich gradient.
CONCLUSIONS: Distinguishing between conditional and unconditional WTP reveals substantial equity implications for vaccination financing. While many mothers are willing to pay something for childhood vaccination, the population-level average WTP has a substantial wealth gradient. An introduction of user fees would need to be accompanied by targeted subsidies and exemption mechanisms to sustain high vaccination coverage in this setting.
METHODS: A cross-sectional cluster sample survey of 400 mothers from 4 rural districts in Tanzania was conducted from June-July 2024. Mothers were asked how much they would be willing to pay for each vaccination if they were no longer freely available. Using a two-part interval regression approach, we estimated the probability of strictly positive WTP (stage one) and the magnitude of WTP among payers (stage two). Conditional (among WTP-positive) and unconditional (population) mean WTP were estimated using parametric log-normal retransformations with Duan’s smearing correction and bootstrapped standard errors. Equity analysis involved comparisons of conditional and unconditional mean WTP across wealth quintiles.
RESULTS: Approximately 85% of respondents indicated a positive WTP. The conditional mean WTP among WTP-positive mothers was TSH 3608 (USD 1.34) (95% CI TSH 3107 - 4510) after applying Duan’s smearing correction (1 USD = 2685 TSH). Unconditional population-average WTP, accounting for zero WTP among a subset of mothers, was substantially lower: TSH 3237 (USD 1.21) (95% CI TSH 2536 - 3837). Both the probability of positive WTP and the unconditional WTP increased monotonically with wealth quintile, reflecting a pro-rich gradient.
CONCLUSIONS: Distinguishing between conditional and unconditional WTP reveals substantial equity implications for vaccination financing. While many mothers are willing to pay something for childhood vaccination, the population-level average WTP has a substantial wealth gradient. An introduction of user fees would need to be accompanied by targeted subsidies and exemption mechanisms to sustain high vaccination coverage in this setting.
Conference/Value in Health Info
2026-05, ISPOR 2026, Philadelphia, PA, USA
Value in Health, Volume 29, Issue S6
Code
P13
Topic
Economic Evaluation
Disease
No Additional Disease & Conditions/Specialized Treatment Areas, SDC: Pediatrics, STA: Vaccines