Background In 2007, a new set of guidelines for blood exposure incidents was introduced in The Netherlands to standardize management and reduce use of hepatitis B immunoglobulin (HBIg). Accidents now have to be assigned into risk categories with the corresponding medical intervention. Aims To study the consequences of the guidelines on overall risk assessment and costs of hepatitis B virus (HBV) prevention. Methods Incidents ( n = 461) from both hospital as well as non-hospital health care workers and others registered by a call centre from the year 2005 were reassessed and reclassified as ‘no-risk’, ‘high-risk’ or ‘low-risk’ according to the corresponding risk categories of the new guidelines. The differences in classification, use of HBV immunoglobulin, source testing and the costs of the HBV prevention strategy were evaluated. Results Of all incidents, 86% could be reassigned directly into the new risk categories. However, there was a significant shift from ‘low-’ to ‘high-risk’ incidents. Overall, administration of HBV vaccination increased and administration of HBIg decreased significantly, although within the group of high-risk incidents, administration of HBIg increased. There was no effect on the frequency of reference serum taken after an incident. While fewer incidents needed intervention, the total costs of HBV prevention still increased by 50%. Total costs increased by 13%, due to a shift in classification. Conclusions The use of the new protocol facilitated standardized risk assessment for blood exposure accidents. HBIg administration and source testing decreased. An increased proportion of high-risk classifications resulted in an increase in the associated costs.