Assessing Contacts' Decision Making on Reducing the Risk of Pertussis Transmission to Newborns Through Immunisation

Inclusion Criteria: * Subjects who the investigator believes that, can and will comply with the requirements of this protocol (ability to understand the study objectives and the questions asked, and ability to operate a computer). * Written informed consent obtained from the subject. * Subjects aged ≥ 18 years at the time of study start who are either: Contacts of newborns (aged ≤ 6 months). OR Expecting mothers in their last trimester of pregnancy or their partners, who will be in close contact with the newborn. • Subjects who will be eligible for pertussis booster vaccination and have not received any pertussis vaccination in the last 2 years (before study start). Exclusion Criteria: * Subjects who have participated in the 'questionnaire design' phase (applicable only for subjects who will participate in the enrollment phase of the study). * Subjects with a contraindication to pertussis vaccination. * Subjects who declare to be in principle against vaccination. * Subjects who declare to be in a chronic physical condition and not compatible with vaccination. * Subjects with a history of pertussis in the last 5 years (before study start). * History of non-response to pertussis vaccination. * Subjects with mental deficiency. * Subjects with unstable chronic health condition(s).