The trivalent influenza vaccine was found effective in children younger than 2 years of age in an observational study in Australia, according to a report published online April 21 in Pediatrics.
Data regarding the vaccine’s effectiveness in this age group are limited, so there is ongoing controversy over whether it should be recommended as routine. To assess the effectiveness of the trivalent influenza vaccine, researchers examined rates of immunization and of influenza-like illness treated at the major pediatric teaching hospital in Perth, Western Australia, during a 4-year period. The vaccine was available for free to all children aged 6-59 months in that state during this interval, said Dr. Christopher C. Blyth of the University of Western Australia and the Princess Margaret Hospital for Children, both in Perth, and his associates, on behalf of the WAIVE (Western Australian Influenza Vaccine Effectiveness) Study Team.
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Despite the efficacy of influenza vaccination in children younger than 2 years of age, debate is ongoing as to whether or not the vaccine should be recommended as routine.
A total of 1,903 children were enrolled in the study. The median age was 1.9 years. Culturing of nasopharyngeal swabs showed that 389 (20.4%) had influenza during the study period and another 1,134 (59.6%) had a different respiratory virus; in the remaining children, the cause of the influenza-like illness was nonviral. The most frequently detected noninfluenza viruses were human picornaviruses (673), respiratory syncytial virus A/B (312), human parainfluenza virus types 1 to 4 (193), adenoviruses B through D (157), bocaviruses (126), and coronaviruses OC43/229E (61); 467 children had two or more viruses detected, including 115 children with influenza.
The overall vaccination uptake was low at 24% for the entire study period, and it decreased significantly during the study interval, from 55.1% during 2008-2009 to 9.7% in 2010-2012. This drop-off was due to the temporary suspension of a preschool vaccination program when the FluVax Junior brand it used was linked to a 44-fold rise in febrile convulsions (BMJ Open. 2011 May 30 [10.1136/bmjopen-2010-000016]).
Despite this decrease in use, vaccine efficacy was evident: It was 64.7% overall and 85.8% among children younger than 2 years, the investigators said (Pediatrics 2014;133:e1218-25).
Even among children who did not receive the full schedule of vaccine doses, vaccine efficacy exceeded 81%. "This study provides the strongest evidence to date supporting the effectiveness of the trivalent influenza vaccine in children younger than 2 years of age," Dr. Blyth and his associates said.
This study was funded by the Western Australian Department of Health. The vaccine was provided by Sanofi Pasteur and CSL Biotherapies. Dr. Peter C. Richmond reported past ties to Baxter and GlaxoSmithKline. Dr. Blyth and the remaining associates reported no relevant financial conflicts of interest.