To assess the anti-PRP antibody response one month after vaccination in the groups receiving a fourth consecutive dose of two formulations of DTPw-HBV/Hib vaccine

All subjects were previously primed with one of the two formulations of the combined DTPw-HBV/Hib vaccine. At the age of 10 months, 50% of each group received a plain PRP challenge to assess the immune memory to PRP. In this booster study in the second year of life, all subjects who received DTPw-HBV/Hib and plain PRP will receive DTPw-HBV as a booster vaccination. All other subjects will receive as booster the same vaccine they received in the primary vaccination study.

Inclusion criteria

• Subjects who the investigator believes that their parents/guardians can and will comply with the requirements of the protocol.
• A male or female of at least 15 months of age at the time of the booster vaccination, who had previously received 3-dose primary vaccination and, if applicable, plain-PRP vaccination.
• Free of obvious health problems as established by medical history and clinical examination before entering the study.

Exclusion criteria for enrolment

• Use of any investigational or non-registered product other than the study vaccine(s) within 30 days preceding the dose of study vaccine, or planned use during the study period.
• Planned administration/ administration of a vaccine not foreseen by the study protocol during the period starting from 30 days before and ending 30 days after administration of study vaccines with the exception of oral polio vaccine (OPV).
• Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to the booster dose.
• Previous booster vaccination against diphtheria, tetanus, pertussis, hepatitis B or Hib with the exception of plain PRP challenge.
• Any confirmed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination.