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.

High levels of antibody in adults three years after vaccination with a reduced antigen content diphtheria-tetanus-acellular pertussis vaccine.

There is increasing interest in prevention of pertussis in adults by vaccination, but little is known about the duration of the antibody response to pertussis, diphtheria or tetanus in reduced antigen content vaccines formulated for adult use. Follow-up of a clinical trial including 550 adults comparing responses to reduced antigen content diphtheria-tetanus-acellular pertussis (dTpa) vaccine, or a licensed Td vaccine, provided the opportunity to evaluate this. Blood samples were collected at 0, 1, 12, 24 and 36 months following vaccination; of the original cohort of 550, 387 subjects (dTpa group N=310, Td+pa group N=77) were tested at month 36.