Immunogenicity and Reactogenicity of a Monovalent Inactivated 2009 Influenza A Vaccine in Adolescents: With Special Reference to Pre-Existing Antibody

The monovalent pandemic vaccine generally was safe, and a single dose of the vaccine given to adolescents induced sufficient immunity. Pre-existing antibody showed substantial effect on antibody response. The effect of pre-existing titer should be considered when evaluating the immunogenicity of influenza vaccines, especially in studies conducted during pandemic waves.