This Article  • Full text  • PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Citation map  • Contact me when this article is cited  Related Content  • Similar articles in JAMA

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

To the Editor: Dr Hoekstra and colleagues¹ report a positive relationship between voucher incentives offered in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and childhood immunization rates. However, the conclusions are biased because the interventions lack clarity, the methods used for calculating outcomes vary, and the analysis failed to control for potential confounders.

Assessment and referral is listed as an intervention, but it occurred at all sites. Monitoring is referred to but never defined. At one point, the authors imply that monitoring involves collecting voucher incentive process data. If so, there cannot be monitoring without voucher incentives. However, if monitoring means assessment and referral, there cannot be voucher incentives without monitoring. Thus, the data may be used to compare voucher incentives plus assessment and referral vs assessment and referral, but they cannot be used to infer the effects of voucher incentives or assessment and referral alone.

. . . [Full Text of this Article]