Risk factors for measles in children aged 8 months–14 years in China after nationwide measles campaign: A multi-site case-control study, 2012–2013

Tuesday, 20th of December 2016

 

Vaccine, Volume 34, Issue 51, 12 December 2016, Pages 6545–6552

Risk factors for measles in children aged 8 months–14 years in China after nationwide measles campaign: A multi-site case-control study, 2012–2013

• Lixin Hao¹ et al.

Vaccine, Volume 34, Issue 51, 12 December 2016, Pages 6553-6560

Excerpts below; full text is at http://www.sciencedirect.com/science/article/pii/S0264410X16001316

Highlights

•Vaccine efficacy of measles containing vaccine in China very high.

•Missed routine vaccination primary risk factor for measles infection in children.

•Lack of timely vaccination linked to recent migration and missed opportunities.

•Similar to infants, hospital exposure strongly associated with measles.

•Strengthened hospital infection control and vaccine outreach efforts required.

Abstract

Introduction

Endemic measles persists in China, despite >95% reported coverage of two measles-containing vaccine doses and nationwide campaign that vaccinated more than 100 million children in 2010. In 2011, almost half of the 9943 measles cases in China occurred in children eligible for measles vaccination. We conducted a case-control study during 2012–2013 to identify risk factors for measles infection in children aged 8 months–14 years.

Methods

Children with laboratory-confirmed measles were age- and neighborhood-matched with three controls. We interviewed parents of case and control infants on potential risk factors for measles. We calculated adjusted matched odds ratios and 95% confidence intervals of risk factors. We calculated attributable fractions for risk factors that could be interpreted as causal and vaccine efficacy (VE) for the measles containing vaccine (MCV) used in the Chinese immunization program.

Results

In all, 969 case-patients and 2845 controls were enrolled. In multivariable analysis, lack of measles vaccination both overall (mOR 22.7 [16.6, 31.1] and when stratified by region (east region, mOR 74.2 [27.3, 202]; central/western regions mOR 17.4 [12.5, 24.3]), hospital exposure (mOR 63.0, 95% CI [32.8, 121]), and migration among counties (overall mOR 3.0 [2.3, 3.9]) were significant risk factors. The calculated VE was 91.9–96.1% for a single dose of MCV and 96.6–99.5% for 2 doses.

Conclusions

Lack of vaccination was the leading risk factor for measles infection, especially in children born since the 2010 supplementary immunization activity. Reducing missed vaccination opportunities, improving immunization access for migrant children, and strengthening school/kindergarten vaccine checks are needed to strengthen the routine immunization program and maintain progress toward measles elimination in China.

1. Introduction

In 2006, China endorsed an action plan to eliminate measles, consistent with the World Health Organization (WHO) Western Pacific Regions goal of measles elimination by 2012. Key components of the plan include achieving and maintaining 2-dose routine measles-containing vaccine (MCV) coverage >95% and conducting supplementary immunization activities (SIAs) to close immunity gaps in children. In China, MCV is given at age 8 months (Measles and Rubella Combined Attenuated Live Vaccine is used) and again between 18 and 23 months of age (Measles, Mumps and Rubella Combined Attenuated Live Vaccine is used), with >95% reported coverage for both doses since 2009 [1]. In 2005, the Chinese State Council (which oversees all Ministries) issued a regulation instituting a requirement that all children have their vaccination records checked at the time of entry to kindergarten and primary school, to ensure that school-age children are—or have been—vaccinated against measles. In practice, children who are not up-to-date with vaccines at the time of school entry are encouraged to be vaccinated, but not excluded from school. During 2004–2009, 27 of 31 provinces conducted unsynchronized province-wide catch-up SIAs [2]. In September 2010, China conducted a synchronized nationwide SIA, with a reported coverage of 97.52% [3], to ensure that all children born during1995–2009 had the opportunity to receive at least 1 dose of MCV regardless of prior vaccination status. As a result, measles incidence decreased dramatically, from 99.5 cases per million people in 2008 to 7.4 in 2011. The drop in reported measles incidence was observed not only in vaccine-targeted children but also among infants under vaccination age and adults [4].

Despite this success, sustained measles virus transmission continues in every province. In 2011, 9943 measles cases were reported nationally. Among these cases, 4574 (46%) were in children aged 8 months through 14 years, who were eligible to receive MCV via the routine schedule or in SIAs conducted during 2004–2010 [4] and [5]. To understand remaining barriers to measles elimination in China after the nationwide 2010 campaign, we conducted a multi-site case-control study during 2012–2013 to identify risk factors for measles infection among different age groups. This paper summarizes results for children aged 8 months–14 years.