Epidemiology of measles before and after measles supplementary immunization in Chongqing

Objective To understand the epidemiological characteristics of measles before and after the implementation of measles supplementary immunization activity (SIA) in Chongqing, and provide evidence for the improvement of measles prevention and control. Methods Descriptive epidemiological analysis was conducted by using the incidence data of measles in Chongqing during 2006-2008 (before the implementation of SIA) and during 2013-2015 (after the implementation of SIA). Results The measles epidemiological characteristics changed after the implementation of measles SIA:the incidence curves was no longer with single peak during 2013-2015 compared with that during 2006-2008, and the incidence season became obviously longer. The cases in urban area increased significantly, accounting for the highest proportion of the total cases during this period. The cases in age group 8 months increased obviously; but the cases in age group 7-14 years due to the SIA in this age group declined. The cases occurred sporadically. Conclusion The decline in the quality of routine immunization and delayed response of outbreaks has resulted in the high incidence of measles. Based on measles epidemiological characteristics, it is necessary to strengthen the surveillance in high incidence season and areas at high risk, improve coverage of the first dose and two doses of measles-containing vaccine, conduct the catch-up activity after checking immunization records to reduce the incidence of measles.