Influenza A/H1N1 MF59-Adjuvanted Vaccine in Preterm and Term Children Aged 6 to 23 Months

OBJECTIVE: This study was designed to evaluate the immunogenicity, safety, and tolerability of a monovalent 2009 pandemic influenza A/H1N1 MF59-adjuvanted vaccine in children aged 6 to 23 months who had different gestational ages (GAs) at birth. METHODS: The study involved 105 children: 35 preterm subjects with a GA of < 32 weeks; 35 preterm subjects with a GA of 32 to 36 weeks; and 35 term subjects with a GA of 37 to 42 weeks. Each child received 2 intramuscular vaccine doses (Focetria [Novartis, Siena, Italy]): dose 1 at enrollment and dose 2 after 4 weeks (28 +/- 2 days). Serum samples for antibody measurements were collected immediately before administration of dose 1, before administration of dose 2 (28 +/- 2 days after baseline), and 4 weeks later (56 +/- 2 days after baseline). Local and systemic reactions were assessed during the 14 days after each vaccination. RESULTS: Of the 101 children who completed the study 32 out of 34 preterm subjects with a GA of < 32 weeks, all of the preterm subjects with a GA of 32 to 36 weeks, and all of the term subjects seroconverted and were seroprotected after the first vaccine dose. Local and systemic tolerability was good in all of the groups, but fever was significantly more common after the first dose than after the second dose (P < .05), and there were no between-group differences. CONCLUSIONS: A single dose of 2009 pandemic influenza A/H1N1 MF59-adjuvanted vaccine evoked a significant immune response against pandemic influenza A/H1N1 virus in children aged 6 to 23 months even if their GA was < 32 weeks. The vaccine had a good safety and tolerability profile. Pediatrics 2011;127:e1161-e1168