Influenza Vaccine Offers "Substantial Benefit" Against Outpatient Illness in Pediatric Populations

Less than one-third of children who tested positive for influenza at a handful of US outpatient clinics between 2011 and 2020 had received the influenza vaccine, according to study results published in Pediatrics.

“Analysis of multiple seasons suggested substantial benefit against outpatient illness,” wrote corresponding author Nicole Hood, MPH, of the Centers for Disease Control and Prevention, Atlanta, Georgia, and coauthors.

The study investigated the effectiveness of inactivated influenza vaccine against outpatient influenza illness in children over a span of 9 influenza seasons. Between the 2011-2012 and the 2019-2020 influenza seasons, children aged 6 months to 17 years with acute respiratory illness seen at five outpatient sites of the US Influenza Vaccine Effectiveness Network were tested for influenza.

Some 28% of 24,148 enrolled children tested positive for influenza: 3017 had influenza A(H3N2), 1459 had influenza A(H1N1)pdm09, and 2178 had influenza B, according to the study. 

The overall rate of influenza vaccination among enrolled children was 39%. Among children tested for influenza, 29% of those who tested positive and 43% of those who tested negative were vaccinated.

The pooled influenza vaccine effectiveness for any type of influenza was 46% across all influenza seasons. Compared with older children, effectiveness against influenza illness was highest among children aged 6 to 59 months. By influenza virus type, the vaccine’s effectiveness was lowest for influenza A(H3N2) infection.

“Investigation of host-specific or virus-related mechanisms that may result in differences by age and virus type/subtype may help further efforts to promote increased vaccination coverage and other influenza-related preventative measures,” researchers advised.

Reference:
Hood N, Flannery B, Gaglani M, et al. Influenza vaccine effectiveness among children: 2011-2020. Pediatrics. 2023;151(4):e2022059922. doi:10.1542/peds.2022-059922