An open clinical trial to study the immune response and safety after giving a booster dose (5th Dose) of a combination vaccine against Diphteria-Tetanus-Pertussis-Polio to healthy adolescents 15-16 Years of age. The first three doses were given during the first year of life, according to the Norwegian child immunization program. The fourth dose was given in a previous clinical trial performed in 1998 when the children were 6-7 years old.

In 2006 there was a change in the child immunization program in Norway: a fourth dose of a Combination Vaccine Against Diphteria-Tetanus-Pertussis-Polio is given to children 6-7 years old.

This study will give us information if there is need for an additional dose (5th dose) of a combination vaccine, containing the pertussis components, before the adolescents are leaving secondary school.

Inclusion Criteria:

• Healthy adolescents who have previously received a dose of a vaccine against diphteria, tetanus, pertussis and polio in a clinical trial in 1998
• Written informed consent from the adolescent and one of his/her parents
• The family must understand norwegian

Exclusion Criteria:

• Serious chronic diseases
• Vaccination against tetanus last 12 months
• Immunization with a Diphteria vaccine component after the study in 1998
• Suspected or confirmed immune deficiency
• Immunological/immunosuppressive treatment
• Pregnancy
• Serious reactions to previous immunization with any of the vaccine components
• Acute fever (axillary temperature ≥ 38°C) at the the of vaccination. (Postpone vaccination)