Psychic vs. Economic Barriers to Vaccine Take-up: Evidence from a Field Experiment in Nigeria

This paper evaluates the relative importance of psychic costs of vaccination compared to monetary costs through a field experiment that randomizes several factors affecting tetanus vaccine take-up among women in rural Nigeria. Although conventional wisdom highlights the relevance of psychic costs, we find no evidence that psychic costs limit vaccine take-up among women who visit clinics. The clinic attendance among women who were incentivized just to show up at a clinic was not different from the attendance among women who were incentivized for vaccination at the clinic. Priming about disease severity increases the perceived severity of disease, but not vaccine take-up. Monetary costs strongly affect vaccination decision. Every year, vaccinations avert two to three million deaths from diphtheria, tetanus, pertussis, and measles worldwide (WHO, 2014). Vaccination is an extremely cost-effective way to improve people’s health. For example, treating one case of measles costs 23 times the cost of one vaccination, and $24 are saved for every $1 spent on the diphtheria-tetanus-pertussis (DTP) vaccine (Ehreth, 2003). Despite these benefits, 22.6 million infants are not sufficiently vaccinated every year, and most of them live in developing countries (WHO, 2014). Given the huge benefits of preventing diseases at low cost, the persistent low vaccine take-up remains a puzzle (for example, see Suk, Lopalco, and Celentano, 2015). This paper reports results of a field experiment explicitly designed to evaluate various potential barriers to vaccine take-up in Nigeria, which is home to 12.8 percent of the world’s unvaccinated infants (WHO, 2014). ∗Sato: National University of Singapore, 21 Lower Kent Ridge Road 04-01, Singapore 119077, [email protected]. Takasaki: University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan 1130033, [email protected]. We are grateful to Abdullahi Belel and the Adamawa State Primary Health Care Development Agency for their cooperation and support throughout the project implementation. We give special thanks to Benjamin Fintan and the field team who devoted themselves to the project. We appreciate Raj Arunachalam, Abhijit Banerjee, Hoyt Bleakley, Esther Duflo, Anne Fitzpatrick, Susan Godlonton, David Lam, Edward Norton, Hitoshi Shigeoka, and Rebecca Thornton for valuable comments. This paper also benefited from feedback from seminar participants at the Informal Development Seminar at the University of Michigan, the Population Association of America, and the University of Tsukuba. This project was supported with research grants from the Institute for Research on Women & Gender, the Rackham Graduate School, the Department of Afroamerican and African Studies, the Department of Economics, and the Center for the Education of Women at the University of Michigan; the Japan Society for the Promotion of Science; and Yamada Scholarship Foundation. Observational studies suggest various reasons for low vaccine take-up, including monetary costs to visit health clinics, such as transportation costs and opportunity costs (Thysen et al., 2014; Uzochukwu et al., 2004); limited information about diseases and vaccinations (Orimadegun et al., 2014); and supply-side constraints, such as vaccine shortages (Santibanez et al., 2012). Furthermore, psychic costs of vaccination, which we define as residuals that cannot be explained by monetary factors, such as beliefs and perceptions about vaccines, could influence vaccination decisions (Pebley et al., 1996; Steele et al., 1996).1 Most extant studies examine barriers to vaccine take-up using qualitative methods, typically by asking respondents their reasons for non-vaccination (DHS 2008; Jheeta and Newell, 2008; Nichter, 1995; UNICEF, 2001). Such observational studies, however, cannot identify the causal effects of potential barriers to vaccination.2 This paper presents a causal examination and compares the behavioral effects of psychic costs and monetary costs on vaccine take-up. The relevance of psychic costs as barriers to vaccination has been commonly documented in Africa. In northern Nigeria, a polio vaccination campaign was famously boycotted by Islamic leaders due to a false rumor that polio vaccines make women infertile or causes them to contract HIV (Jegede, 2007). This distrust of vaccine efficacy led to a widespread refusal to receive polio vaccinations among the general population. Similar incidents opposed tetanus vaccination campaigns in Cameroon in 1990 (Feldman-Savlesberg, 2008) and polio vaccination campaigns in Kenya, Uganda, and Tanzania (UNICEF, 1997). These episodes have led to conventional wisdom: a presumption commonly held by researchers that psychic costs of vaccination are large barriers to vaccine take-up (Rainey, 2010). No causal studies, however, have systematically examined this conventional wisdom. If psychic costs of vaccination actually hinder vaccine take-up, then policy interventions can potentially promote vaccine take-up by reducing these psychic costs. An option would be to increase the perceived costs of disease by emphasizing its severity (i.e., priming). In contrast, if psychic costs of vaccination are not major barriers to vaccine take-up, such priming interventions would be ineffective. Thus, it is of critical importance to identify the psychic costs of vaccination. Our randomized experiment conducted among women in rural Nigeria captures monetary costs and psychic costs separately as potential barriers to their tetanus vaccine take-up. To capture monetary costs as potential barriers to vaccination, we randomized the amount of cash transfers provided to women conditional on their clinic attendance. To capture psychic costs of vaccination, a group of women received their cash transfers further conditional on receiving a vaccine. Because the only difference between these two conditions is whether or not one is required to receive a vaccine for cash rewards, the difference in clinic attendance between these two conditions captures the psychic costs of vaccination. To examine the effect of priming on vaccination, we also randomized a disease message: either a “scared-straight” message, which emphasizes the severity of tetanus, or a control message, which provides the same information on tetanus without the emphasis of the disease severity.3 Examples of beliefs and perceptions about vaccines as psychic costs of vaccination include fear of needles; fear of vaccine safety, such as side effects; misperceptions about vaccines, such as the belief that vaccines might give a person HIV or other diseases; and religious beliefs against vaccines. Currie (2006) reviews the literature that examines the effects of stigma on the take-ups of social benefits in developed countries, where stigma is defined as disutility arising from participating a welfare program (Moffitt, 1983). Currie (2006) concludes that stigma is not a large barrier to participating in social benefits programs. Although this provides suggestive evidence that stigmas has a small effect on benefit uptake, none of the studies reviewed provide causal evidence. “Scared straight” originally referred to a program that intended to deter juveniles from future crimes by