Vaccine Hesitancy and Refusal: Behavioral Evidence from Rural Northern Nigeria

"It is widely believed that vaccine hesitancy is prevalent in African countries, although this belief is without rigorous evidence."

Vaccine hesitancy - defined in this paper as the non-uptake of vaccines despite their availability due to non-monetary factors directly associated with vaccination - is believed to be a critical issue in African countries. The Nigerian polio immunisation boycott in 2003, which was precipitated by religious and political leaders who sowed the seeds of distrust, contributed to the creation of persistent vaccine hesitancy in the region. The field experiment reported in this paper was explicitly designed to measure vaccine hesitancy behaviourally by offering free tetanus vaccines on the doorstep to women of childbearing age in rural Nigeria.

The study was conducted in October 2016 in 41 villages in the Jada local government area (LGA) of Adamawa state in the northeastern region of Nigeria. A woman was eligible to participate if she was aged between 15 and 35 and had never received a tetanus vaccine. Of 1,249 sampled women, 599 formed the analysis sample; the others were excluded due to refusal, absence, and ineligibility due to an inaccurate census list. Respondents were randomly assigned to either the treatment or control group. The task for women in the control group was to answer a simple set of questions, posed by nurses at the women's homes, related to vaccination. The task among women in the treatment group was to receive the vaccination at their house (to eliminate any potential hesitancy to visit clinics), in addition to answering the same questions as the control group.

To receive the vaccination, women in the treatment group were asked to submit a voucher. As it turned out, even if they did not submit the voucher, they had a chance to receive the vaccine at no cost if they orally accepted. The purpose of the voucher system and surprise offer of vaccine was to evaluate differences in respondents' willingness to pay (WTP) for the vaccine among respondents in the treatment arm. Distinct from a conventional way of eliciting WTP through people's self-reporting (stated preference), this study captured the WTP from women's actual behaviours (revealed preference).

According to the voucher submission and the actual vaccine take-up among respondents in the treatment group, the researchers categorised women into three types: (i) accepter (a respondent who submitted the voucher and received the vaccine after responding to the follow-up survey), (ii) floating refuser (a respondent who did not submit the voucher in advance but agreed to receive the vaccine at no cost after responding to the follow-up survey), and (iii) absolute refuser (a respondent who did not submit the voucher and did not receive the vaccine after responding to the follow-up survey, even though accepting the surprise offer of the vaccine without submitting the voucher involved no cost).

The study finds that the prevalence of vaccine hesitancy is about 13%. The vaccine hesitaters were almost equally divided between absolute refusers and floating refusers. Common self-reported reasons for not receiving the vaccine among women in the treatment group were that the vaccine is painful (73.3%), the vaccine is not necessary (56.7%), the vaccine is harmful (30.0%), and the vaccine is not effective (26.7%). Although the number of observations is small due to missing values, these results provide suggestive evidence that physical pain might be as important as a barrier to vaccination as distrust or negative belief.

Overall, the study found that association of subjective beliefs about vaccination and actual vaccination behaviours was limited: Weak correlations were found only for a small number of subjective measures. That is, women's beliefs only weakly corresponded to their behaviours. "This result suggests a limitation to an observational approach, ...and emphasizes the importance of an experimental approach to measure the prevalence of vaccine hesitancy."

The implication is that a simple intervention, such as a door-to-door vaccination campaign that makes the cost of vaccination low enough, may be effective for floating refusers. In contrast, to induce behavioural change among absolute refusers, policies first need to lower the barriers directly associated with vaccines, such as misperception and distrust of vaccines. The finding of the similar prevalence of absolute refusers and floating refusers suggests that two distinct sets of policies for each group to be reached are equally needed.