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 signifi-cantly 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.