From RCT to Real-World Impact:
How Demand-Side Interventions Help Close the Immunization Gap
On May 21, 2026, Nobel Laureate Esther Duflo, Professor Arun Chandrasekhar, and teams from J-PAL and Evidence Action walked through the evidence base for demand-side immunization interventions and the work now underway to translate these findings into a pilot in Nigeria. The recording and slides from the session are available below.
The science of reaching every child
A landmark RCT in Haryana, India — published in Econometrica — tested 75 intervention combinations across nearly 300,000 children. The most cost-effective package (text reminders + community ambassadors) increased full immunizations by 26%; adding incentives in low-coverage areas raised rates by 44%.
This workshop brought together the researchers behind these findings and the team now piloting them in Nigeria, where over half of missed vaccinations stem from awareness gaps. Attendees heard directly from Nobel Laureate Esther Duflo and Professor Arun Chandrasekhar.
Download the slide decks
Adapting the evidence for Nigeria
Nigeria houses the highest number of unvaccinated (8.7M) and zero-dose children in the world (2.1M). UNICEF surveying shows that low demand is one of the most critical barriers to Nigeria's vaccination gap, indicating that of those who miss vaccine doses, 50% attribute it to awareness gaps, 40% to immunization not being a priority, and 12% to long distances among reasons for missed doses. Evidence Action and J-PAL are collaborating to adapt and pilot the intervention packages tested in Haryana, combining reminders, information hub ambassadors, and targeted incentives, in two Nigerian states.
Evidence Action has been delivering health interventions in Nigeria since 2016, successfully delivered the community ambassador model at scale before, and is already reaching pregnant women with SMS messages.
The workshop explored how Evidence Action is building on the Haryana study and broader evidence in the ecosystem to address Nigeria's underimmunization crisis.
Pilot at a glance
Three papers, one study ecosystem
These papers are the source of the evidence discussed in the workshop. Click to expand each for a brief summary.
The primary paper from the Haryana study. Researchers cross-randomized three interventions — incentives, SMS reminders, and community ambassadors — across 140 primary health centers and 755 subcenters serving ~295,000 children. This produced 75 unique treatment combinations.
Rather than reporting results for each combination individually, the authors developed a machine-learning method (Treatment Variant Aggregation) to identify which packages were most effective and most cost-effective. This is the methodological innovation that makes this study unusual — and what will be a focus of the workshop.
Read the full paper →| Location | 7 low-coverage districts in Haryana, India |
| Scale | 295,038 children; 471,608 vaccines administered |
| Timeline | 2016–2018 |
| Baseline full immunization | ~39% (parent-reported); <20% on-time measles |
| Outcome measure | Measles vaccine receipt (proxy for schedule completion) |
This paper establishes the theoretical and empirical foundation for the ambassador component. In two experiments — 213 villages in Karnataka and 521 villages in Haryana — researchers tested whether community-nominated "gossips" could spread information more effectively than randomly selected individuals, influential leaders, or trusted advisors.
The key finding: simply asking a few villagers who is good at spreading information was an easy, inexpensive, and reliable way to identify network-central individuals who then drove meaningful behavior change. In Haryana, villages with information hub ambassadors saw 22% more children vaccinated monthly. These nominated individuals were central in a network sense — not just popular or powerful.
Read the full paper →A 3ie evidence impact summary presenting the results of the RCT testing each of the three interventions — reminders, information-hub ambassadors, and incentives — and their combinations across Haryana. This summary translates the research findings for a policy and practitioner audience.
Read the impact summary →