A quasi-experimental evaluation of a financial incentive for first-dose COVID-19 vaccination among adults aged ≥ 60 years in South Africa

  1. Candice M Chetty-Makkan
  2. Harsha Thirumurthy
  3. Elizabeth F Bair
  4. Simamkele Bokolo
  5. Candy Day
  6. Korstiaan Wapenaar
  7. Jesse Werner
  8. Lawrence Long
  9. Brendan Maughan-Brown
  10. Jacqui Miot
  11. Sophie J S Pascoe
  12. Alison M Buttenheim

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Abstract

Introduction

COVID-19 vaccination coverage in South Africa (RSA) remains low despite increased access to vaccines. On November 1, 2021, RSA introduced the Vooma Voucher program which provided a small guaranteed financial incentive, a Vooma Voucher redeemable at grocery stores, for COVID-19 vaccination among older adults, a population most vulnerable to serious illness, hospitalization, and death. However, the association of financial incentives with vaccination coverage remains unclear.

Methods

We evaluated the association of the conditional economic incentive program with first-dose vaccination rates among adults (aged ≥60 years) through a quasi-experimental cohort study. The Vooma Voucher program was a nationwide vaccination incentive program implemented for adults aged ≥60 years from November 1, 2021 to February 28, 2022. We ran interrupted time series models to evaluate the Vooma Voucher program at national and provincial levels. We used data between October 1, 2021 and November 27, 2021 in models estimated at the daily level. Individuals who received their first vaccine dose received a text message to access a ZAR100 ($∼7) voucher that was redeemable at grocery stores.

Results

The Vooma Voucher program was associated with a 7.15-12.01% increase in daily first-dose vaccinations in November 2021 compared to late October 2021. Overall, the incentive accounted for 6,476-10,874 additional first vaccine doses from November 1-27, 2021, or 8.31-13.95% of all doses administered to those aged ≥60 years during that period. This result is robust to the inclusion of controls for the number of active vaccine delivery sites and for the nationwide Vooma vaccination weekend initiative (November 12-14), both of which also increased vaccinations through expanded access to vaccines and demand creation activities.

Conclusions

Financial incentives for COVID-19 vaccination led to a modest increase in first dose vaccinations among older adults in RSA. Financial incentives and expanded access to vaccines may result in higher vaccination coverage.

Trial registration number (SANCTR)

DOH-27-012022-9116

Key points (3-5 sentences)

What is already known about this topic?

There is a lack of evidence on whether financial incentives for COVID-19 vaccinations are effective in low- and middle-income countries.

What does this study add?

We found that a ZAR100 (∼US$7) incentive for adults aged ≥60 years increased additional first vaccine doses between November 1-27, 2021 to those aged ≥60 years during that period.

How this study might affect research, practice or policy?

Small guaranteed financial incentives may be an effective strategy to increase vaccine demand among older adults in low- and middle-income countries.

Article activity feed

  1. Version published to 10.1101/2022.05.06.22274712v3 on medRxiv
  2. ScreenIT

    SciScore for 10.1101/2022.05.06.22274712: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Although the Vooma Voucher program continued until February 28, 2022, the announcement of the Omicron variant on November 24, 2022 would likely confound the effect of the incentive program on days that followed the announcement.
    Vooma Voucher
    suggested: None
    Analyses were conducted using Stata 17.0 (StataCorp, College Station, TX).
    StataCorp
    suggested: (Stata, RRID:SCR_012763)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    A key limitation is the assumption in our ITS models there were no other factors that coincided with the introduction of the Vooma Voucher program and affected vaccine demand. The robustness of our findings to the inclusion of supply and demand creation measures, and to provincial and weekly specifications, increases confidence in our findings. Another limitation is that we only study short-term effects of the incentive program, as the announcement of the Omicron variant made it challenging to study effects of incentives beyond that date. Given the vulnerability of older adults to serious illness, hospitalization, and death as a result of COVID-19, identifying effective strategies to increase vaccine demand is crucial. More generally, as LMICs struggle to achieve sufficiently high vaccine demand despite expansions in vaccine delivery and access, our findings suggest that small financial incentives may be effective in increasing vaccination coverage.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a protocol registration statement.

    Results from scite Reference Check: We found no unreliable references.

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  3. Version published to 10.1101/2022.05.06.22274712v2 on medRxiv
  4. Version published to 10.1101/2022.05.06.22274712v1 on medRxiv