In 2009 and 2010, a series of measles outbreaks, involving different age groups, occurred in rural areas of the Chabahar district in southeast Iran. These outbreaks raised questions regarding the effectiveness of immunization programs in these areas. To determine the most important factors leading to these outbreaks, and to determine the effectiveness of the measles vaccination program, the present study analyzed surveillance data and performed a case-control study. The total number of reported cases during the study period was 126. The estimated vaccine effectiveness, based on the adjusted odds ratio of the case-control study, was 74.2% (95% CI, 10.2-92.6). On two occasions, both primary and secondary cases of the outbreaks were vaccinated school children. In total, 42% of all cases were aged above 7 years, and 6.3% were above 20 years. With regard to the important role of schools as the foci of contact between uninfected and infected children, supplementary immunization of children before starting in school could be effective in preventing measles outbreaks. In addition, implementation of supplementary immunization every 5-10 years in older age groups might be effective in preventing future outbreaks.