Beginning with the winter season of 2004-2005, influenza vaccination has been recommended for all children 6 to 23 months old in the United States. However, its safety in young children has not been adequately studied in large populations. A study was conducted by Simon J. Hambidge to screen for medically attended events in the clinic, emergency department, or hospital after administration of trivalent inactivated influenza vaccine in children 6 to 23 months old.
Retrospective cohort using self-control analysis, with chart review of significant medically attended events at 8 managed care organizations in the United States that comprise the Vaccine Safety Datalink. Participants were all children in the Vaccine Safety Datalink cohort 6 to 23 months old who received trivalent inactivated influenza vaccine between January 1, 1991, and May 31, 2003 (45 356 children with 69 359 vaccinations).
Any medically attended event significantly associated with trivalent inactivated influenza vaccine in risk windows 0 to 3 days, 1 to 14 days (primary analysis), 1 to 42 days, or 15 to 42 days after vaccination, compared with 2 control periods, one before vaccination and the second after the risk window. All individual ICD-9 codes as well as predefined aggregate codes were examined.
Before chart review, only 1 diagnosis, gastritis/duodenitis, was more likely to occur in the 14 days after trivalent inactivated influenza vaccine (matched odds ratio [OR], 5.50; 95% confidence interval [CI], 1.22-24.81 for control period 1, and matched OR, 4.33; 95% CI, 1.23-15.21 for control period 2). Thirteen medically attended events were less likely to occur after trivalent inactivated influenza vaccine, including acute upper respiratory tract infection, asthma, bronchiolitis, and otitis media. After chart review, gastritis/duodenitis was not significantly associated with trivalent inactivated influenza vaccine (matched OR, 4.00; 95% CI, 0.85-18.84 for control period 1; matched OR, 3.34; 95% CI, 0.92-12.11 for control period 2).
In the largest population-based study to date of the safety of trivalent inactivated influenza vaccine in young children, there were very few medically attended events, none of which were serious, significantly associated with the vaccine. This study provides additional evidence supporting the safety of universally immunizing all children 6 to 23 months old with influenza vaccine.
Author Affiliations: Clinical Research Unit, Kaiser Permanente Colorado (Drs Hambidge, Glanz, France, McClure, Xu, and Yamasaki), Community Health Services, Denver Health, and Department of Pediatrics, University of Colorado School of Medicine (Dr Hambidge), and Department of Preventive Medicine and Biostatistics, University of Colorado School of Medicine (Drs Hambidge, Glanz, and France), Denver; Center for Health Studies, Group Health Cooperative, Seattle, Wash (Dr Jackson); Center for Health Research, Northwest Kaiser Permanente, Portland, Ore (Dr Mullooly); UCLA Center for Vaccine Research, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Calif (Dr Zangwill); Southern California Kaiser Permanente, Panorama City (Dr Marcy); Kaiser Permanente Vaccine Study Center, Northern California Kaiser Permanente, Oakland (Dr Black and Mr Lewis); University of California, San Francisco (Dr Shinefield); Marshfield Clinic Research Foundation, Marshfield, Wis (Dr Belongia); Health Partners Research Foundation, Minneapolis, Minn (Dr Nordin); Centers for Disease Control and Prevention, Atlanta, Ga (Drs Chen, Shay, Davis, and DeStefano).