HealthDay News — The 2018 to 2019 influenza vaccine effectiveness (VE) was about 40% to 60% for reducing pediatric influenza A-associated hospitalizations and emergency department visits, according to a study published online in Pediatrics.

Angela P. Campbell, MD, MPH, from the US Centers for Disease Control and Prevention in Atlanta, and colleagues tested children aged 6 months to 17 years with acute respiratory illness for influenza using molecular assays. Vaccination status was examined based on parental report, state immunization information systems, and/or provider reports. VE was estimated using a test-negative design comparing the odds of vaccination for children testing positive vs negative for influenza.

The researchers found that 13% of 1792 inpatients were influenza-positive: 47%, 36%, 9%, and 7% for influenza A(H3N2), A(H1N1)pdm09, A (not subtyped), and B viruses, respectively. Twenty-two percent of the 1944 children with emergency department visits were positive for influenza: 48%, 35%, 11%, and 5% for A(H3N2), A(H1N1)pdm09, A (not subtyped), and B viruses, respectively. VE was 41% against any influenza-related hospitalizations: 41% and 47% for A(H3N2) and A(H1N1)pdm09, respectively. VE was 51% against any influenza-related emergency department visits: 39% and 61% against A(H3N2) and A(H1N1)pdm09, respectively.

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“The vaccine was ~40% effective against A(H3N2)-related hospitalizations and emergency department visits, even in a season when antigenically drifted clade 3C.3a influenza viruses were the predominant circulating A(H3N2) viruses,” the authors write.

Several authors disclosed financial ties to the pharmaceutical industry.

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