BMC Infectious Diseases
(Accessed 24 January 2015)
Measles vaccine coverage estimates in an outbreak three years after the nation-wide campaign in China: implications for measles elimination, 2013
Chao Ma1†, Fangjun Li2†, Xiang Zheng3, Hong Zhang2, Mengjuan Duan1, Yanhua Yang2, Lixin Hao1, Qiru Su1, Lance Rodewald4, Bosong Guo5, Shanliang Xiao6, Huaqing Wang1, Li Li1, Junhua Li2, Huiming Luo1* and Lidong Gao2*
BMC Infectious Diseases 2015, 15:23 doi:10.1186/s12879-015-0752-z
Published: 22 January 2015
China is approaching measles elimination, but indigenous measles still circulates. County L in China has reported measles-containing vaccine (MCV) coverage rates >95% since 2000. Despite high reported coverage, a large measles outbreak occurred among young children in L County. We measured MCV coverage using 5 different methods during an investigation on this outbreak and compared our estimates with reported rates.
Reported coverage rates are determined by aggregating clinic-based data across the county: doses administered in each clinic divided by the number of children registered in each clinic. Our methods estimated coverage for the 2010?2012 birth cohort, and were (1) administrative method: doses administered in clinics divided by the birth cohort recorded in the Statistical Year Book, (2) house-to-house convenience-sample survey of children living near cases, (3) vaccination clinic records review, (4) determination of a convenience sample of measles outbreak cases? vaccination statuses and using the field vaccine efficacy outbreak equation to estimate population coverage, and (5) a seroprevalence survey using a convenience sample of residual blood samples from hospitals.
The measles outbreak totaled 215 cases, representing an incidence of 195.8 per million population. Our estimated MCV coverage rates were: (1) administrative method: 84.1%-87.0% for MCV1 and 80.3%-90.0% for MCV2, (2) in-house survey: 83.3% of 9?17 month children received MCV1, and 74.5% of 24?47 month children received MCV2, (3) clinic record review: 85.5% of 9?17 month children received MCV1, and 73.2% of 24?59 month children received MCV2, (4) field VE method: 83.6% of 9?47 month children received one or more MCV doses, and (5) serology: seropositive rates were <80% in the 12?17 and 18?23 month age cohorts.
Compared with reported coverage >95%, our 5 coverage assessments all showed substantially lower coverage. China should evaluate guidelines for reporting vaccination coverage and identify feasible improvements to the assessment methods.