We aimed to determine the proportion of the population in Madang (Papua New Guinea) immune to measles infection by age groups, with respect to immunization status and study location, using dried blood sampling technology. We performed a prospective cross-sectional sero-survey. Population immunity against measles was sub-optimal (77%) and reported measles vaccine coverage in children <10 years of age was low (41%). The urban population was more susceptible to measles infection, compared with the rural population (66% vs 79% immune, aOR=0.6, p=0.05). Sero-conversion and long term protection rates appeared to be higher when at least one dose of vaccine was provided at or after 12 months of age (84% vs 59%, aOR=4.3, p=0.004). Such a dose is, however, not currently prescribed by the national immunization schedule.