Financial incentives for COVID-19 vaccines in a rural low-resource setting: a cluster-randomized trial

Abstract

We implemented a clustered randomized controlled trial with 6,963 residents in six rural Ghana districts to estimate the causal impact of financial incentives on coronavirus disease 2019 (COVID-19) vaccination uptake. Villages randomly received one of four video treatment arms: a placebo, a standard health message, a high cash incentive (60 Ghana cedis) and a low cash incentive (20 Ghana cedis). For the first co-primary outcome-COVID-19 vaccination intentions-non-vaccinated participants assigned to the cash incentive treatments had an average rate of 81% (1,733 of 2,168) compared to 71% (1,895 of 2,669) for those in the placebo treatment arm. For the other co-primary outcome of self-reported vaccinations 2 months after the initial intervention, the average rate for participants in the cash treatment was 3.5% higher than for participants in the placebo treatment (95% confidence interval (CI): 0.001, 6.9; P = 0.045): 40% (602 of 1,486) versus 36.3% (672 of 1,850). We also verified vaccination status of participants: in the cash treatment arm, 36.6% (355 of 1,058) of verified participants had at least one dose of the COVID-19 vaccine compared to 30.3% (439 of 1,544) for those in the placebo-a difference of 6.3% (95% CI: 2.4, 10.2; P = 0.001). For the intention and the vaccination outcomes, the low cash incentive (20 Ghana cedis) had a larger positive effect on COVID-19 vaccine uptake than the high cash incentive (60 Ghana cedis). Trial identifier: AEARCTR-0008775 .

Fig. 1. CONSORT diagram for the Ghana Financial Incentives Trial. Phase I: Treatment.

Phase II/III: a, Post-treatment survey; b, Spillover Sample. Phase IV: Verification of Vaccination Status. D1 through D6 denotes districts.

Fig. 2. Financial incentive and vaccination outcomes.

Odds ratios for model estimates in Table 3. Odds ratios are reported for the logistic regressions for the three outcome variables: vaccine intention (models 1 and 2 in Table 3), reported vaccination (models 3 and 4 in Table 3) and verified vaccination (models 5 and 6 in Table 3). These outcomes are regressed on dummy variables indicating whether individuals received one of the cash incentive videos (Cash) or the health message (Health); the estimation includes the full set of covariates. The 95% CIs are reported for each odds ratio. Observations are in parentheses: model 1 (5,644); model 2 (5,644); model 3 (3,957); model 4 (3,957); model 5 (2,146); and model 6 (2,146).

Extended Data Fig. 1

Balance on Standardized Mean Differences for Full Phase I Sample: Unadjusted compared to propensity score weighted sample.

Extended Data Fig. 2

Randomization Inference Simulated Odds Ratios for Models in Table 3. (Vertical red line indicating observed odds ratio).

Extended Data Fig. 3

BART: Heterogeneous Treatment Effects (Food Spending and Age).

Extended Data Fig. 4

BART: Heterogeneous Treatment Effects (Gender, WhatsApp and Education).