Outbreak response immunisation: The experience of Chad during recurrent measles epidemics in 2005 and 2010.

Despite impressive gains in measles control globally, measles epidemics continue to occur in countries with insufficient vaccination coverage. WHO guidelines now recommend outbreak response immunisation (ORI) for controlling measles outbreaks in certain contexts. The objective of this study was to describe late and early response vaccination activities during two consecutive measles outbreaks that occurred in 2005 and 2010 in N'Djamena, Chad. Using Lot Quality Assurance Sampling, vaccination coverage was estimated to be low before the interventions. Following mass vaccination campaigns, measles cases declined. The timeliness and quality of ORI activities are crucial determinants of success. However, effective outbreak response should be accompanied by strong routine vaccination programmes to ensure sustainable high vaccination coverage.