Subjects were previously vaccinated with either Boostrix or a control Td vaccine in study NCT00109330. Only subjects who were part of the primary study will be invited to participate in this study. All subjects will receive a single dose of Boostrix at Visit 1 (Day 0) and subjects will be observed till Visit 2 (Day 30) for safety in terms of solicited adverse events (during 4 days post vaccination), unsolicited adverse events (during 31 days post vaccination) and serious adverse event (during the trial period). A blood sample will be collected from all subjects before vaccination (Visit 1) and one month after vaccination (Visit 2) for antibodies estimation.