['The goal was to assess the impact of influenza vaccine clinical alerts on missed opportunities for vaccination and on overall influenza immunization rates for children and adolescents with asthma.', 'A prospective, cluster-randomized trial of 20 primary care sites was conducted between October 1, 2006, and March 31, 2007. At intervention sites, electronic health record-based clinical alerts for influenza vaccine appeared at all office visits for children between 5 and 19 years of age with asthma who were due for vaccine. The proportion of captured immunization opportunities at visits and overall rates of complete vaccination for patients at intervention and control sites were compared with those for the previous year, after standardization for relevant covariates. The study had >80% power to detect an 8% difference in the change in rates between the study and baseline years at intervention versus control practices.', 'A total of 23 418 visits and 11 919 children were included in the study year and 21 422 visits and 10 667 children in the previous year. The majority of children were male, 5 to 9 years of age, and privately insured. With standardization for selected covariates, captured vaccination opportunities increased from 14.4% to 18.6% at intervention sites and from 12.7% to 16.3% at control sites, a 0.3% greater improvement. Standardized influenza vaccination rates improved 3.4% more at intervention sites than at control sites. The 4 practices with the greatest increases in rates (>or=11%) were all in the intervention group. Vaccine receipt was more common among children who had been vaccinated previously, with increasing numbers of visits, with care early in the season, and at preventive versus acute care visits.'] Does impact of electronic health record-based alert on influenza vaccination for children with asthma?