Changes of epidemiological characteristics of measles in Beijing before and after supplementary immunization campaigns of measles vaccine in 2010

To investigate the changes of epidemiological characteristics of measles in Beijing before and after Supplementary Immunization Campaigns (SIA) (2007-2010 vs 2011-2014) of measles-containing vaccine (MCV) among children aged between 8 months and 14 years in 2010.Descriptive epidemiological analysis was conducted on surveillance data of measles cases (clinical cases and laboratory confirmed cases), with the occurrence during 2007-2014, and of outbreaks, with the occurrence during 2009-2014, from National Notifiable Disease Reporting System. MapInfo geographic information system (Version 8.5) was used to illustrate the distribution of measles incidence by district. Annual measles incidence was classified into 5 groups at the same intervals between the upper and lower limits to analyze the morbidity of the different areas.In total, 7 722 and 3 132 measles cases were reported during 2007-2010 and 2011-2014, with the annual incidence of 11.59 and 3.84 cases per 100 000 population, respectively. Comparing with the results during 2007-2010, total number of measles cases and average annual incidence during 2011-2014 were decreased by 59.4%, and 66.9%, respectively. Among measles cases during 2011-2014, percentage of cases aged 15 years or above were 57.7%(56/97), 62.0%(49/79), 65.5%(370/565), and 71.4% (1 707/2 391), respectively, which increased by years. During 2007-2010, the highest risk age for adults was 20-34, while 2011-2014, 5 years older: 25-39. During 2009-2010, 2011-2012, and 2013-2014, 50.3% (447/889), 30.3% (10/33), and 57.8% (201/348), respectively, of measles cases aged 8-17 months were unvaccinated by MCV. Percentages of measles cases aged 0-7 months, 8 months-14 years, 15-39 years and 40 years or above during 2013-2014, who visited hospitals 7-21 days before disease onset, were 59.8% (238/398), 49.3% (237/481), 32.2% (529/1641), and 37.6% (164/436), respectively. A total of 11 nosocomial measles outbreaks occurred during 2013-2014, which was much higher than that during 2009-2010 (2 nosocomial outbreaks). And universities accounted for the majority of outbreak settings of schools (3/4). All 11 outbreaks among grouped employees during 2009-2012 occurred in factories, restaurants, or large shopping centers, while the largest proportion (6/16) of that kind of outbreaks during 2013-2014 occurred in office buildings.SIA of MCV in 2010 effectively decreased measles transmission in Beijing. But routine immunization of MCV still needed to be improved. The issue of adult measles has been a prominent problem. Hospitals, office buildings and universities were the focus of prevention of measles transmission.