Immunogenicity of a reduced dose of A/H3N2 in the 2005 southern hemisphere formulation of inactivated split influenza vaccine.

Background: The 2005 southern hemisphere formulation of the inactivated split-virion influenza vaccine Vaxigrip unintentionally contained a lower concentration of haemagglutinin (HA) than European Pharmacopoeia (EP) and WHO specifications for one of the three strains.

Objectives: To evaluate the immunogenicity of the 2005 southern hemisphere formulation of an influenza vaccine containing 9 microg/dose of HA for A/Wellington/1/2004(H3N2) strain, and 15 microg/dose for each of the A/New Caledonia/20/99(H1N1) strain and B/Shanghai/361/2002-like strains.

Patients/methods: In an open, non-controlled multicentre clinical trial, 75 healthy adults (18-59 years) and 65 healthy older adults (> or =60 years) were vaccinated once.