I2. Pediatric Vaccines
Flor M. Munoz, MD
Associate Professor of Pediatrics
Baylor College of Medicine
Disclosure: Biocryst: Grant/Research Support
CDC: Research Grant
Moderna: Other Financial or Material Support, Safety Monitoring Board Member/Chair
NIH: Research Grant
Novavax: Research Grant
UP to Date: Author and Editor - Royalties, Other Financial or Material Support
Lara Danziger-Isakov, MD, MPH
Professor of Pediatrics
Cincinnati Children's Hospital Medical Center
Disclosure: Ansun: Research Grant
Astellas: Grant/Research Support
GlaxoSmithKline: Advisory Board
Merck: Consultant, Grant/Research Support
Shire: Grant/Research Support
Viracor: Grant/Research Support
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
Background : Pediatric hematopoietic cell transplant (HCT) recipients often fail to have robust responses to influenza (flu) vaccine. We conducted a blinded phase II trial comparing high-dose (HD) trivalent inactivated vaccine (TIV) vs standard dose (SD) quadrivalent inactivated vaccine (QIV).
Children 3-17 years old and 3-35 months post-allogeneic HCT were enrolled at 9 centers and randomized to either 2 doses of HD-TIV or SD-QIV during the 2016-17 flu season. We compared immune responses by hemagglutination inhibition (HAI) from children 3-11 (early) vs 12-35 (late) months (m) post-HCT to 3 common flu vaccine antigens, irrespective of vaccine type. HAI responses were evaluated at baseline (visit 1), 1 m post dose 1 (visit 2) and dose 2 (visit 3), and 7 m post dose 2 (visit 4). Geometric mean titers (GMT) were adjusted for baseline log-titer values.
Thirty-one children, median age 11 (7-15) years, were enrolled; 17 (55%) were immunized early and 14 (45%) late. Over 50% of patients had a potentially seroprotective (≥1:40) HAI titer at baseline, with no significant difference post-vaccination between early and late subjects. Table 1 compares early vs late subjects with HAI seroconversion (4-fold HAI titer rise). Post dose 1, late subjects, compared with early, had higher rates of seroconversion to all influenza strains. Post dose 2, early subjects, compared with late, had increased seroconversion. Late subjects had higher GMTs for H1N1 post dose 1 & 2, H3N2 after dose 1, and strain B/VIC post dose 1 & 2 (Figure 1). Although immunogenicity waned throughout flu season, higher seroconversion rates and GMT to H3N2 and strain B/VIC were retained in late subjects.
Conclusion : Compared to subjects in early post-HCT group, late post-HCT subjects had better flu vaccine immune responses as noted by higher GMT and HAI seroconversion. However, 2 doses seemed more beneficial in the early post-HCT group. Future analyses are underway, including comparing immunogenicity of HD vs SD flu vaccine.