I2. Pediatric Vaccines
Oral Abstract Submission
Janet A. Englund, MD
Seattle Children's Hospital/Univ. of Washington
Disclosure: AstraZeneca: Grant/Research Support
Chimerix: Grant/Research Support
GlaxoSmithKline: Consultant, Grant/Research Support
Meissa Vaccines: Consultant
Merck: Grant/Research Support
Novavax: Grant/Research Support
Sanofi Pasteur: Consultant
Christopher J. Harrison, MD
Professor of Pediatrics
Children's Mercy Hospital
Kansas City, MO
Disclosure: GlaxoSmithKline: Grant/Research Support, Research Grant or Support
Merck: Grant/Research Support, Research Grant or Support
Pfizer: Scientific Research Study Investigator, Research Grant or Support
Sanofi Pasteur: Consultant
Annual national estimates of influenza vaccine effectiveness (VE) typically measure protection against outpatient medically attended influenza illness. We assessed influenza VE in preventing laboratory-confirmed influenza hospitalization in children across two influenza A(H3N2)-predominant seasons.
Children < 18 yrs hospitalized with acute respiratory illness were enrolled at 7 pediatric hospitals in the New Vaccine Surveillance Network. We included subjects >= 6 mos with <= 10 days of symptoms enrolled during the 2016-17 and 2017-18 seasons (date of first through last influenza positive case for each site). Combined mid-turbinate and throat swabs were tested using molecular assays. We estimated age-stratified VE from a test-negative design using logistic regression to compare the odds of vaccination among cases positive for influenza with controls testing negative, adjusting for age, enrollment month, site, underlying comorbidities, and race/ethnicity. Full/partial vaccination were defined using ACIP criteria. We verified vaccine receipt from state immunization registries and/or provider records.
Among 3441 children with complete preliminary data, in 2016-17, 156/1710 (9%) tested positive for influenza: 91 (58%) with influenza A(H3N2), 5 (3%) with A(H1N1), and 60 (38%) with B viruses. In 2017-18, 193/1731 (11%) tested positive: 87 (45%) with influenza A(H3N2), 47 (24%) with A(H1N1), and 58 (30%) with B. VE for all vaccinated children (full and partial) against any influenza was 48% (95% confidence interval, 26%–63%) in 2016-17 and 45% (24%-60%) in 2017-18. Combining seasons, VE for fully and partially vaccinated children against any influenza type was 46% (32%-58%); by virus, VE was 30% (4%-49%) for influenza A(H3N2), 71% (46%-85%) for A(H1N1), and 57% (36%-70%) for B viruses. There was no statistically significant difference in VE by age or full/partial vaccination status for any virus (Table).
Vaccination in the 2016-17 and 2017-18 seasons nearly halved the risk of children being hospitalized with influenza. These findings support the use of vaccination to prevent severe illness in children. Our study highlights the need for a better understanding of the lower VE against influenza A(H3N2) viruses.