Is the Intention to Vaccinate Enough? Systematic Variation in the Value of Timely Vaccinations and Preferences for Monetary vs Non-monetary Incentives among Pregnant Women in Southern Tanzania

"Sustained progress towards global vaccination targets requires overcoming, or compensating for, incrementally greater barriers to vaccinating hard-to-reach and hard-to-vaccinate children."

Incentives, which are grounded in behavioural economics, have been used to encourage diverse health-related behaviours, including vaccinations. The decision of a parent to vaccinate their child reveals an implicit value of the vaccination (implicit willingness to pay; WTP) that exceeds the costs, whether reflective of individual or systemic barriers. For some individuals, subsidies in the form of incentives may be used to align individual and social preferences by "tipping the scale" toward making timely vaccination a utility-maximising choice. This study prospectively assessed pregnant women's valuations of routine childhood vaccinations and preferences for alternative incentives. The ultimate goal was to inform a digital health intervention aiming to increase vaccination coverage and timeliness in southern Tanzania.

Between August and December 2017, 406 pregnant women in their last trimester of pregnancy, aged 16 or older and with access to a mobile phone, were enrolled in the study. Surveys included questions in a triple-bounded dichotomous choice format that assessed participants' WTP or their willingness to accept (WTA) compensation in exchange for getting their child vaccinated on time. Women were also asked to rank 6 incentive options for each timely vaccination of their children.

The value of a vaccination was defined in this study as a function of women's knowledge and beliefs regarding vaccinations as a means of protecting children against disease. Vaccinations are freely available in health facilities throughout the study area; therefore, the cost of vaccinations primarily consists of transportation cost and the opportunity cost of time.

All women indicated they expected to get their children vaccinated according to the recommended schedule, even without a monetary incentive, thus precluding an analysis of the distribution of potential subsidies needed to ensure the timely vaccination of children. That said, WTP was lower for women with greater vaccine hesitancy scores, those unable to name at least one vaccine-preventable disease, and those familiar with vaccine-related side effects. Lower WTP was also associated with lower education and fewer household assets, a prior birth, and a residence in rural areas with greater travel times to the nearest health facility.

When asked to rank alternative incentives for getting their children vaccinated on time, women tended to prefer non-monetary incentives, such as a birth certificate, a maternal health check, or, to a lesser extent, a pharmacy voucher, over monetary incentives such as a lottery ticket with a monetary pay-out, a mobile money payment, or mobile phone credit.

Policy implications of the findings include:

• In the Tanzanian setting, the implicit costs of vaccinations, combined with vaccine hesitancy, may be "tipping the scale" for a subset of women against the timely vaccination of their children. That is, unexpected system-level barriers are likely to be the primary drivers of missed or delayed vaccinations in this setting. Such barriers may include the complexity of the vaccination schedule, providers' communication and responsiveness to scheduled time-sensitive appointments for patients, and supply-side barriers. Additional research should focus on exploring means of reducing unexpected and implicit costs to mothers.
• Owing to the strong associations of WTP with vaccine hesitancy and knowledge, there appear to be information deficits among pregnant women that may suggest a role for antenatal care visits as a means of improving vaccine knowledge and preempting vaccine hesitancy. Similarly, the associations of WTP with household assets and travel time to the nearest health facility highlight potential access barriers and suggest a role for expanded hours, reduced waiting time, advance notification of stock-outs, and mobile vaccination clinics.
• Additional research is needed to characterise the mechanisms underlying this study's findings indicating preference for non-monetary incentives and to inform the design of incentive structures and policies with maximum impact on parents' vaccination decisions.

The researchers stress that there are trade-offs with respect to the ethics and practicality of rewards, incentives, or payments for health services in low-resource settings. For example, there is evidence that extrinsic motivators hold potential to crowd out intrinsic motivators, and attention must be paid to potential adverse consequences of incentivising behaviours that may already be governed by "social contracts" - e.g., expectations of herd immunity. "Ethical and cost-effectiveness considerations at the population level, and the extent to which behavioral economics can inform the optimal design of incentive structures for mothers and providers, thus merit careful deliberation."

In conclusion: "The results suggest that women value vaccinations for their children, but also support differentiated interventions such as continued efforts to mitigate access barriers, information campaigns to highlight benefits and correct misperceptions about vaccinations, and non-monetary incentives to compensate for system-level barriers to timely vaccinations. The methods may be applied to other vaccines, populations, and settings, and may inform ongoing efforts to rapidly vaccinate large populations against SARS-CoV-2."