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Letters designed with behavioural science increase influenza vaccination in Medicare beneficiaries


The influenza (‘flu’) vaccination is low cost1 and effective, typically reducing the likelihood of infection by 50–60%2. It is recommended for nearly everyone older than 6 months of age3; yet, only 40% of Americans are immunized each year. Vaccination rates are higher among at-risk groups, such as those ≥65 years of age, but still only 6 in 10 receive it4. There have been numerous attempts to improve vaccination rates using strategies such as school-based programmes, financial incentives and reminders, but these have generally had limited success5,6,7. Of the attempts that are successful, most are expensive—limiting scalability—and have not been evaluated in the elderly8. Conversely, lower-cost interventions, such as mailed information, hold promise for a scalable solution, but their limited effectiveness may result from how they have been designed. We randomly assigned 228,000 individuals ≥66 years of age to one of five versions of letters intended to motivate vaccination, including versions with an implementation intention prompt and an enhanced active choice implementation prompt. We found that a single mailed letter significantly increased influenza vaccination rates compared with no letter. However, there was no difference in vaccination rates across the four different letters tailored with behavioural science techniques.

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Fig. 1: Study participants and randomization scheme.
Fig. 2: Enhanced active choice implementation intention prompt included in the arm 5 letter.

Data availability

Restrictions apply to the availability of the raw data, which were used under data use agreements for the current study and therefore cannot be shared publicly. However, data may be available upon reasonable request and permission of the vendor.


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This project would not have been possible without the collaboration of the White House’s Social and Behavioral Sciences Team (SBST), the General Service Administration’s Office of Evaluation Sciences, the National Vaccine Program Office and the Centers for Medicare and Medicaid Services (CMS) at the US Department of Health and Human Services. We especially thank G. Brill, M. Donneyong, B. Gellin, T. A. Johnson, B. Luca and B. Sivak. We also thank The Laura and John Arnold Foundation for generous financial support. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. This work was supported by an unrestricted grant from the Laura and John Arnold Foundation.

Author information




D.Y. and N.K.C. contributed to the study conception and design and interpretation of the results. J.C.L. prepared and analysed the data. D.Y. and J.C.L. contributed to manuscript drafting. N.K.C. and R.G. provided interpretation of the results and critical manuscript revisions.

Corresponding author

Correspondence to Niteesh K. Choudhry.

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The authors declare no competing interests.

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Supplementary Figure 1, Supplementary Tables 1–5

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Yokum, D., Lauffenburger, J.C., Ghazinouri, R. et al. Letters designed with behavioural science increase influenza vaccination in Medicare beneficiaries. Nat Hum Behav 2, 743–749 (2018).

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