Clinical and immune responses to inactivated influenza A(H1N1)pdm09 vaccine in children
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Published on: December 1, 2017
Karen L Kotloff1, Natasha B Halasa, Christopher J Harrison
1From the *Division of Infectious Disease and Tropical Pediatrics, Department of Pediatrics, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD; †Department of Pediatrics, Vanderbilt Vaccine Research Program, Vanderbilt University School of Medicine, Nashville, TN; ‡Department of Pediatrics, Pediatric Infectious Diseases Section, Children's Mercy Hospital and Clinics, and the University of Missouri-Kansas City, Kansas City, MO; §Division of Pediatric Infectious Diseases, Department of Pediatrics, University of Washington and Seattle Children's Hospital, Seattle, WA; ¶Department of Pediatrics, Duke Clinical Vaccine Unit, Duke University School of Medicine, Durham, NC; ‖Division of General Pediatrics, Department of Pediatrics, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD; **Department of Medicine, Duke University School of Medicine, Durham, NC; ††Southern Research Institute, Birmingham, AL; and ‡‡EMMES Corp, Department of Vaccines and Infectious Diseases, Rockville, MD.
Insights
The inactivated influenza A(H1N1)pdm09 vaccine is safe for children, but younger children need two doses for protection. Further research is needed for single-dose vaccines for young children during pandemics.
Area of Science:
- Pediatric infectious diseases
- Vaccinology
- Public health
Background:
- The 2009 influenza A H1N1 pandemic caused significant illness and death in children, necessitating vaccination.
- Children were a priority group for H1N1 vaccination due to high morbidity and mortality.
- This study evaluated an inactivated influenza A(H1N1)pdm09 vaccine in children.
Purpose of the Study:
- To assess the safety and immunogenicity of an inactivated influenza A(H1N1)pdm09 vaccine.
- To evaluate different vaccine dosages (15 µg and 30 µg hemagglutinin antigen) in children.
- To determine age-specific immune responses and safety profiles in children aged 6 months to 17 years.
Main Methods:
- A multicenter, randomized, double-blind, age-stratified trial.
- Two doses of vaccine administered 21 days apart.
- Assessment of reactogenicity, adverse events, and serious adverse events.
- Measurement of serum hemagglutination inhibition titers to evaluate immunogenicity.
Main Results:
- The vaccine was generally well-tolerated with no vaccine-related serious adverse events.
- The 15 µg dose achieved seroprotective hemagglutination inhibition (≥ 1:40) in 78% of 6-35 month olds and 98% of 10-17 year olds after two doses.
- The 30 µg dose showed similar immune responses.
- Younger children (6-35 months) required two doses for adequate protection, unlike older children (10-17 years).
Conclusions:
- The inactivated influenza A(H1N1)pdm09 vaccine demonstrated a favorable safety profile in children at both tested dosages.
- While older children achieved adequate immunity with one dose, younger children required two doses.
- There is a need for well-tolerated vaccines that can induce single-dose immunity in young children for pandemic preparedness.
Background:
As the influenza A H1N1 pandemic emerged in 2009, children were found to experience high morbidity and mortality and were prioritized for vaccination. This multicenter, randomized, double-blind, age-stratified trial assessed the safety and immunogenicity of inactivated influenza A(H1N1)pdm09 vaccine in healthy children aged 6 months to 17 years.
Methods:
Children received 2 doses of approximately 15 or 30 µg hemagglutin antigen 21 days apart. Reactogenicity was assessed for 8 days after each dose, adverse events through day 42, and serious adverse events or new-onset chronic illnesses through day 201. Serum hemagglutination inhibition titers were measured on days 0 (prevaccination), 8, 21, 29 and 42.
Results:
A total of 583 children received the first dose and 571 received the second dose of vaccine. Vaccinations were generally well-tolerated and no related serious adverse events were observed. The 15 µg dosage elicited a seroprotective hemagglutination inhibition (≥ 1:40) in 20%, 47% and 93% of children in the 6-35 month, 3-9 year and 10-17 year age strata 21 days after dose 1 and in 78%, 82% and 98% of children 21 days after dose 2, respectively. The 30 µg vaccine dosage induced similar responses.
Conclusions:
The inactivated influenza A(H1N1)pdm09 vaccine exhibited a favorable safety profile at both dosage levels. While a single 15 or 30 µg dose induced seroprotective antibody responses in most children 10-17 years of age, younger children required 2 doses, even when receiving dosages 4- to 6-fold higher than recommended. Well-tolerated vaccines are needed that induce immunity after a single dose for use in young children during influenza pandemics.
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