Measles vaccine coverage estimates in an outbreak three years after the nation-wide campaign in China: implications for measles elimination 2013

Monday, 27th of June 2016

Measles vaccine coverage estimates in an outbreak three years after the nation-wide campaign in China: implications for measles elimination 2013

• Chao Ma^†
• Fangjun Li^†
• Xiang Zheng
• Hong Zhang
• Mengjuan Duan
• Yanhua Yang
• Lixin Hao
• Qiru Su
• Lance Rodewald
• Bosong Guo
• Shanliang Xiao
• Huaqing Wang
• Li Li
• Junhua Li
• Huiming Luo
• Lidong Gao

Abstract

Background

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.

Methods

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.

Results

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.

Conclusions

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.