The purpose of this long-term follow-up of a Phase I study is to evaluate the kinetics of the antibody response to NTHi-Mcat antigens and long-term safety, in subjects aged between 50-71 years at the time of enrolment in the NTHi-Mcat-001 study. These subjects were previously exposed to two adjuvanted formulations of the NTHi-Mcat vaccine administered according to a 0, 2 months schedule in the NTHi-Mcat-001 (201281) study. The subjects that had received saline placebo controls will also be included in this follow-up study to make comparisons with the investigational vaccines. No vaccinations will be administered in this trial.