Booster vaccination of adults with reduced-antigen-content diphtheria, Tetanus and pertussis vaccine: immunogenicity 5 years post-vaccination.

At 60 months post-vaccination, adults (mean age 45.6 years) randomised to receive combined reduced-antigen-content diphtheria-tetanus and acellular pertussis vaccine (dTpa) versus tetanus-diphtheria (Td)+monovalent acellular pertussis (pa) were seroprotected against diphtheria (> or =0.016IU/mL Vero cell assay) and tetanus (> or =0.1IU/mL ELISA assay) in 94.4% and 96.2%, respectively (dTpa), compared with 93.7% and 90.6% (Td+pa). Anti-FHA, anti-PT and anti-PRN antibodies (> or =5EL.U/mL) were maintained in 100%, 89.5% and 95.0% of dTpa versus 100%, 85.5% and 90.6% of pa vaccine recipients. At 5 years post boosting, antibody levels to diphtheria and tetanus are similar amongst adults receiving a dTpa or dT, and pertussis antibodies remain above pre-booster levels in at least 85%.

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. Serum samples were obtained on D0 and 21 for haemagglutination inhibition (HAI) antibody titration. RESULTS: A high proportion of adults (64%) and elderly (68%) were already seroprotected (HAI titre of > or =40) against A/Wellington/1/2004(H3N2) before vaccination, probably due to high circulation of an antigenically similar H3N2 strain and a high 2004 vaccination rate. By D21, seroprotection rates against H3N2 attained 93.8% and 96.0% in adults and elderly respectively. The other two immunogenicity criteria for annual licensure of influenza vaccines in Europe were also met in both age groups for the H3N2 strain, and also for the H1N1 and B strains. CONCLUSIONS: These results enabled the 2005 southern hemisphere vaccine to be used in expectation that it would provide satisfactory protection against influenza, despite the reduced H3N2 antigen content.

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. Following a decrease in antibody levels against all vaccine antigens between one and 24 months following vaccination, levels stabilized during the third year, remaining higher at 36 months than pre-vaccination for all vaccine antigens. In particular, more than 90% of subjects remained seropositive for pertussis toxin and pertactin antibodies at 36 months after vaccination, suggesting ongoing protection against pertussis. Adult-formulated dTpa vaccines could replace Td for routine booster vaccination of older individuals.