Impact of financial incentives on documented immunization rates in the inner city: Results of a randomized controlled trial

Objective. - This study determined the effect of 2 financial incentives - bonus and enhanced fee-for-service - on documented immunization rates during a second period of observation. Methods. - Incentives were given to 57 randomly selected inner-city physicians 4 times at 4-month intervals based on the performance of 50 randomly selected children. Coverage from linked records from all sources was determined for a subsample of children within physician offices. Results. - Up-to-date coverage rates documented in the charts increased significantly for children in the bonus group (49.7% to 55.6%; P < .05) and the enhanced fee-for-service group (50.8% to 58.2%; P < .01) compared with the control group. The number of immunizations given by these physicians did not change significantly, although the number of immunizations given by others and documented by physicians in the bonus group did increase (P < .05). Up-to-date coverage for all groups increased from 20 to 40 percentage points when immunizations from physician charts were combined with other sources. Conclusions. - Both financial incentives produced a significant increase in coverage levels. Increases were primarily due to better documentation not to better immunizing practices. The financial incentives appeared to provide motivation to physicians but were not sufficient to overcome entrenched behavior patterns. However, true immunization coverage was substantially higher than that documented in the charts.