Use of the influenza vaccine in children 6 to 23 months is not associated with an increased risk for a medical visit for any serious conditions, according to a study in the October 25 issue of JAMA.
Influenza is a leading vaccine-preventable cause of illness and death in the United States. Children younger than 2 years experience higher rates of illness from influenza than any other age group except individuals older than 65 years, according to background information in the article. Until recently, the trivalent inactivated influenza vaccine was recommended only for adults and children with known chronic medical conditions that could put them at higher risk from influenza infection, such as asthma. But based on the increasing evidence of high rates of illness from influenza infection in young children, the Centers for Disease Control and Prevention recommended use of this vaccine in all children 6 to 23 months old, including healthy children with no chronic medical condition, beginning in the winter season of 2004-2005. By January 31, 2005, 48 percent of all children in this age group in the United States had received trivalent inactivated influenza vaccine. However, its safety in young children has not been adequately studied in large populations.
Simon J. Hambidge, M.D., Ph.D., of Kaiser Permanente Colorado, Denver, and colleagues evaluated the safety of trivalent inactivated influenza vaccine in a large population of children 6 to 23 months old. The researchers analyzed data on significant medically attended events that occurred after vaccination, during "risk windows", compared with events that occurred in two control periods, one before vaccination and the second after the risk window. These medically attended events, such as acute respiratory tract infection, asthma, cough and pneumonia, were reviewed at eight managed care organizations in the United States that comprise the Vaccine Safety Datalink. The participants received trivalent inactivated influenza vaccine between January 1, 1991, and May 31, 2003 (45,356 children with 69,359 vaccinations).
The researchers found that no conditions were significantly more likely to occur within either the 3-day, the 1- to 42-day, or the 15- to 42-day risk windows compared with both control windows. During the 1-14 day risk window, there was a very slight increase in visits for mild vomiting and diarrhea to outpatient doctor's clinics, but less visits for asthma, cough, and the common cold.
"While our findings offer reassurance regarding the safety of the vaccine in the youngest children, large safety studies of influenza vaccine in children in the newly recommended age group of children 3 to 5 years old are needed. Our study, the largest safety study of trivalent inactivated influenza vaccine in children aged 6 to 23 months, adds to prior evidence that influenza vaccine is safe in infants and young children," the authors conclude.
(JAMA. 2006;296:1990-1997. Available pre-embargo to the media at www.jamamedia.org.)
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