Randomized, Multicenter Trial of a Single Dose of AS03-adjuvanted or Unadjuvanted H1N1 2009 Pandemic Influenza Vaccine in Children 6 Months to <9 Years of Age: Safety and Immunogenicity

Langley JM et al. – AS03–adjuvanted H1N1 2009 pandemic influenza vaccine (3.75 ug or 1.9 ug HA), administered as 2 doses, was highly immunogenic, induced long–term immune response to 6 months, with a clinically acceptable safety profile in children aged 6 months to <9 years of age.

Methods

• Three hundred twenty-two healthy children 6 months to <9 years of age were randomized to receive 2 doses of nonadjuvanted (15 µg or 7.5 ug HA) or adjuvanted vaccine (3.75 ug HA/AS03A or 1.9 ug HA/AS03B), 21 days apart.
• Blood samples before and after each dose were tested for immune responses using hemagglutination inhibition and microneutralization assays. Safety assessments were done up to day 385.

Results

• The first dose of both AS03-adjuvanted vaccines elicited strong immune responses (seroprotection rates: 98.3%/99.0%; seroconversion rates: 94.9%/97.0%; geometric mean fold rises: 36.2/33.6), which were higher post-dose 2 (seroprotection rate: 100.0%/100%; seroconversion rate: 100.0%/98.8%; geometric mean fold rise: 157.1/151.6), meeting European regulatory criteria on days 21 and 42.
• The nonadjuvanted 15 µg HA vaccine also met the regulatory criteria after each dose; the 7.5 ug HA vaccine met them only post-dose 2. Six months post-dose 1, all vaccines except the nonadjuvanted 7.5 ug HA vaccine met European regulatory criteria.
• Neutralizing antibody response paralleled the hemagglutination inhibition immune response after each dose.
• Pain at the injection site, lasting 2–3 days, was more common following adjuvanted than nonadjuvanted vaccination.

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