I2. Pediatric Vaccines
Oral Abstract Submission
Manjusha Gaglani, MBBS
Director, Center for Research in Vaccines and Infections (CRVI); Josephine Ballard Endowed Research Chair and Professor of Pediatrics; Chief, Pediatric Infectious Diseases
Baylor Scott & White Health
Disclosure: Janssen (Johnson & Johnson): Other Financial or Material Support
Medimmune/AstraZeneca: Other Financial or Material Support
Arnold Monto, MD
Professor of Epidemiology, Global Public Health; Thomas Francis, Jr. Collegiate Professor of Public Health
University of Michigan
Ann Arbor, MI
Disclosure: Sanofi Pasteur: Other Financial or Material Support
Seqirus: Other Financial or Material Support
Background : Studies have demonstrated that optimal protection against childhood influenza requires two “priming” doses of influenza vaccine in the first season of vaccination. Two doses of influenza vaccine are recommended for US children aged 6 months – 8 years who received ≤1 dose in prior seasons. We examined risk of influenza among children fully or partially vaccinated during study seasons and vaccine effectiveness (VE) by number of priming doses.
Methods : Analyses included children aged 6 months – 17 years enrolled during outpatient visits for acute illness for ≤7 days with cough in the US Influenza Vaccine Effectiveness Network during 2014–2015 through 2017–2018. Participants’ respiratory specimens were tested for influenza by rRT-PCR. Vaccination histories back to birth year were obtained from electronic immunization records. VE was calculated by comparing vaccination odds among influenza-positive cases to test-negative controls, as 100 x (1- odds ratio) adjusted for season, site, age, high-risk status, and calendar time.
Results : Of 7583 children, 6362 (84%) had received ≥1 dose in their lifetime. Among vaccinated children, 90% were primed prior to the enrollment season, and 80% were primed prior to age 2 years. Most (55%) received two priming doses in their first season. Among children recommended to receive two priming doses in the enrollment season, receipt of two doses versus one was associated with a lower risk of influenza illness (aOR: 0.60; 95%CL: 0.36, 1.00). VE of ≥1 dose in the enrollment season against any influenza among unprimed children was 53% (95%CL: 36, 66). VE of ≥1 dose in the enrollment season was similar among children primed with one dose in their first season, (46%; 95%CL: 34, 55) and among those primed with two doses (46%; 95%CL: 35, 55). Overall results were similar when stratified by age and for A/H3N2 viruses, which predominated during study years.
Conclusion : Among US children recommended to receive two priming doses of vaccine in the enrollment season, receipt of two doses provided optimal protection. VE in seasons after the priming did not differ by number of priming doses. Results were driven by predominance of A/H3N2 viruses and may not be similar for A/H1N1pdm09 or B viruses. Current US influenza vaccine recommendations for children are effective and appropriate.