Optimal Design for Scaling Childhood Immunization Bracelets: Experimental evidence from Sierra Leone

Context: With the introduction of a malaria vaccine in April 2024 in all districts except Freetown (Western Urban district), the vast majority of children in Sierra Leone are now due for 10 immunization visits: at birth (BCG, oral polio), 6 weeks (Penta 1+), 10 weeks (Penta 2+), 14 weeks (Penta 3+), 6-months (Malaria 1), 7-months (Malaria 2), 8-months (Malaria 3), 9-months (Measles 1, Yellow Fever), 15-months (Measles 2), and 18 months (Malaria 4). As of June 2024, children residing in Western Area Urban (Freetown) are not eligible for the malaria vaccine. These children continue to have a six-visit immunization schedule. Given the recent introduction of the malaria vaccine, there is uncertainty around if and when the malaria vaccine may be offered to children in Freetown.

Intervention: We will provide children with colorful bracelets that indicate their progress through the immunization schedule. These colorful bracelets serve as social signals. They may also provide information about the new vaccine’s availability and take-up in their community. In both bracelet treatments children will receive a first bracelet at their first vaccine visit, a signaling bracelet for timely completion of all vaccines up to Measles 1, and a final bracelet for timely completion of all immunizations through Malaria 4, the last of the new ten-visit schedule. In one of the bracelet treatments, we will also incentivize the first malaria vaccine dose at 6 months with an additional bracelet.

Nurses-in-charge of each study clinic will be invited to a district-level training introducing them to the bracelets and study. They will subsequently receive comprehensive training on the implementation of the bracelets at their clinic. Community Health Workers (CHWs) assigned to each clinic will receive cascade training from their supervisor to disseminate information about the bracelets and their meaning as part of their door-to-door activities in their communities.

Innovations for Poverty Action field staff will visit the clinic to monitor the quality of the implementation a couple of weeks after the clinic-based training, and approximately every three to four months thereafter.

2024-06-20

2026-12-31

1. Number of vaccines received on time, defined as coming within 2 months of each vaccine’s due date.
2. Number of vaccines by 20 months* independent of timeliness.
3. Number of malaria doses received by 20 months.

*We will extend this window to 24 months if we secure additional funding. Twenty-four months is the ideal timeframe to capture the possible convergence between the control and treatment groups.

1. Vaccination outcomes:
- Number of measles doses by 20 months.
- Share of children completing malaria and measles vaccines on time, on time, defined as coming within 2 months of a vaccine’s due date, for the following vaccines: BCG due at birth; Penta 1, 2 and 3 due at 1.5, 2.5 and 3.5 months; Malaria 1, 2 and 3 due at 6, 7 and 8 months; Measles 1 and 2 due at 9 and 15 months; Malaria 4 due at 18 months.
- Share of children completing malaria and measles vaccines by the time they are 20 months old, for the following vaccines.

2. Other vaccine-related outcomes:
- Knowledge about the malaria vaccine’s availability, schedule, eligibility criteria.
- Social norms around completion of the malaria vaccine (views about caregivers who complete the malaria vaccine visits timely versus not).
- Perception of the malaria vaccine’s importance and safety.
- Frequency and intensity of vaccination outreach activities at the clinic level.

3. Other non-vaccine related outcomes:
- Vitamin-A supplementation (VAS) timeliness at 6, 12 and 18 months.
- Non-vaccine-related malaria prevention behavior (e.g. use of bed net).

Government clinics in the selected districts will be randomly assigned into one of three study arms:

1) Three-bracelet arm: Clinic staff distribute three differently colored bracelets. A yellow bracelet is given at the 1st immunization visit. The yellow bracelet will be exchanged for a purple bracelet when a child comes for all visits up until the first dose of measles on time. The bracelet will be exchanged for a multicolor bracelet if the child comes for all visits up until the last malaria dose on time. The bracelets show whether a child has completed the 8 required immunization visits within one year on time, and completed all visits required within two years on time.

2) Four-bracelet arm: Clinic staff distribute four differently colored bracelets. A yellow bracelet is given at the 1st immunization visit. The yellow bracelet will be exchanged for an orange bracelet when the child comes for the first malaria vaccine visit. The orange bracelet will be exchanged for a purple bracelet when a child comes for all subsequent malaria vaccine visits and the first dose of measles on time. The bracelet will be exchanged for a multicolor bracelet if the child comes for all visits up until the last malaria dose on time. The bracelets show whether a child has initiated the malaria vaccine series, completed the 8 required immunization visits within one year on time, and completed all visits required within two years on time.

3) Control group: No bracelets are given.

If the malaria vaccine is rolled out in Freetown, we will introduce the signaling bracelets in a random set of clinics in Western Area districts. We randomly assigned a set of clinics in these districts to the three-bracelet treatment or the control.

Not available

Randomization done by a computer.

Randomization is performed at the level of Peripheral Health Units (PHUs, a.k.a health clinics) and stratified by district, clinic type and size. Specifically, we stratify the randomization by whether a clinic is i) a Community Health Center, ii) any other PHU type with a population larger than the 70th percentile of clinics, iii) any other PHU type with a population lower or equal to the 70th percentile of clinics.

Primary health unit (PHU)

Yes

255 PHUs (clinics)

We will capture immunization data for 12 monthly cohorts of children in each of our study clinics. For the latest vaccine, we will capture outcomes for 3 cohorts who will be old enough to have received the malaria 4 vaccine and be assessed for completion of the full immunization schedule. Maximum sample - full immunization rate under one year and timeliness for vaccines 1-8: N = 255 (clinics) x 12 (monthly birth cohorts) x 15 (average birth cohort size) = 45,900 caregivers. Minimum sample - full immunization rate under two years and timeliness for vaccines 9 and 10: N = 255 x 3 x 15 = 11,475 caregivers.

85 health clinics control, 85 health clinics 3-bracelet treatment, 85 health clinics 4-bracelet treatment.