Background Booster seat legislation may decrease the burden of motor vehicle occupant injury in children 4–9 years old.

Methods We examined rates of hospitalisations for motor vehicle (MV) occupant-related injuries, seatbelt-related injuries and MV occupant-related fatalities in Canadian children, comparing provinces with legislation (Ontario 2005, Quebec 2003) to those without. Hospital discharge data was obtained for 1994–2005 from the Discharge Abstract Database (DAD) and the Hospital Morbidity Database (HMDB). Death data was obtained from the Traffic Accident Information Database (TRAID). Population based injury and death rate ratios were calculated and changes from 1994 to 2005 were determined.

Results There were a total of 3920 MV occupant-related hospitalisations and 358 MV occupant-related fatalities in Canadian children aged 4–9. In 2005, after legislation, Ontario had a significantly lower rate of hospitalisation for MV occupant-related injuries (RR=0.49 (95% CI 0.35 to 0.63)). Rates of hospitalisations and fatalities declined from 1994 to 2005 across all provinces regardless of legislation status. Ontario had significantly higher rate reductions and a consistently lower annual rate of MV occupant-related hospitalisations than other provinces. Injury and death rates were higher in Quebec and increased after legislation was introduced.

Discussion Results indicate heterogeneity between the two provinces with booster seat legislation. The simple presence of booster seat legislation is not sufficient to decrease the burden of motor vehicle occupant injuries.