Willingness to pay for three hypothetical malaria vaccines in Nigeria

Abstract

Background: Unlike some African countries that have reported a ∼50% reduction in malaria deaths in recent years, Nigeria has shown no evidence of a systematic decline in malaria burden. An important and sustainable reduction in malaria burden cannot be achieved unless an effective and inexpensive malaria vaccine becomes available. Objectives: The goals of this study were to determine the willingness to pay (WTP) for 3 hypothetical malaria vaccines with different levels of protection (in years), effectiveness, and adverse effects; and to identify factors that influence the price that people are willing to pay in Nigeria. Methods: With the aid of a questionnaire, a contingent valuation method using payment cards was used to elicit WTP values for 3 hypothetical malaria vaccines. Payment cards contained both a description of the features of the vaccine being evaluated and price options. The 3 hypothetical vaccines had the following characteristics: vaccine A was 75% effective, protected for 3 years, and was well tolerated; vaccine B was 85% effective, protected for 6 years, and was less well tolerated than vaccine A; and vaccine C was 95% effective and protected for 12 years, but was the least well tolerated. Participants consisted of a convenience sample of individuals who were at the pharmacy waiting area of the state-owned hospitals located in Benin City and Warri, Nigeria. Every third patient or caregiver who was in the pharmacy to fill a prescription was asked to take part in the study as they waited to see the pharmacist. If consent was not granted, the next person in line was approached to be interviewed. Linear multiple regression analysis and nonparametric Kruskal-Wallis, Mann-Whitney, or χ 2 test was applied in inferential analysis, where necessary, to investigate the effects of sociodemographic factors on WTP. Prices on payment cards were expressed in Nigerian naira (NGN 150.00 ≈ US $1.00), but study results were expressed in US dollars. Results: A total of 359 individuals aged ≥18 years of 500 who were approached agreed to participate in the study, giving a response rate of 71.8%. Most of the participants (216/359; 60.2%) were women, and 48 of them were pregnant. Most respondents (299/359; 83.3%) had at least one malaria attack within the last year, and 27.3% (98/359) were hospitalized for malaria. The mean WTP for vaccine A was $6.77 and that for vaccine B was $6.70. Vaccine C was the least well accepted with a mean WTP of $5.06. Respondents were willing to pay significantly more for vaccine A (95% CI, $5.96–$7.57); thus, the WTP was significantly different for the 3 hypothetical malaria vaccines (P < 0.001; Kruskal-Wallis statistic [kw] = 84.304). Dunn's multiple comparison test also indicated that the WTP values for vaccines A and B were significantly different from each other (P < 0.05). There was also a significant difference between vaccine A or B versus C (P < 0.001). All workers and those with a higher monthly income were willing to pay significantly more for vaccines A and B, but less for C (P < 0.003). Those who preferred vaccine A (198/359; 55.2%) were willing to back their choice with a higher WTP (P < 0.001). Conclusions: It appears that although malaria is a serious disease, the Nigerian people in this sample preferred and were willing to pay more for a vaccine that was well tolerated, even if its effectiveness and duration of protection against malaria were lower than those of a product that caused severe adverse effects. Interpretation of this study should be guided by the knowledge that differences exist between the study sample and the general population. ( Clin Ther. 2010;32:1533–1544) © 2010 Excerpta Medica Inc.