The impact of supplementary immunization activities on the epidemiology of measles in Tianjin, China

Abstract

Summary Objectives China has repeatedly used supplemental immunization activities (SIAs) to work towards measles elimination, but it is unknown if the SIAs are reaching non-locals, migrants from rural to urban areas. This study characterizes temporal trends in measles incidence by local and non-local residency and evaluates the impact of SIAs on measles incidence in Tianjin, China. Methods Daily measles case counts were tabulated separately by residency. These two datasets were combined so that each day had two observations. We conducted Poisson regression using generalized estimating equations with an exchangeable working correlation structure to estimate rate ratios (RRs). Results There were 12,465 measles cases in Tianjin over the 10-year period. The rate of measles was higher in non-locals than locals before the 2008 SIA (RR: 3.60, 95% CI: 3.27, 3.96), but this attenuates to a RR of 1.22 between the 2008 and 2010 SIAs (95% CI: 1.02, 1.45). Following the 2010 SIA, non-locals had a lower rate of measles (RR: 0.78, 95% CI: 0.69, 0.87). Conclusions The disparity in measles incidence between locals and non-locals was reduced following two SIAs. Sustained public health interventions will be needed to maintain low measles incidence among non-locals given ongoing migration of people throughout China.

The measles epidemic trend over the past 30 years in a central district in Shanghai, China

“…Similar to the results of many other studies, the significant increase of the incidence of measles was mainly due to the high incidence of measles among migrants with low vaccine coverage [ 10 – 13 ]. The incidence of measles in migrants was several times higher than that of local residents in recent years in the Jing’an District.…”

Measles Antibodies in Mother–Infant Dyads in Tianjin, China

“…At 3 months of age, almost all infants lack a protective titer of maternal antibodies, regardless of the antibody titer in their mothers. These findings are important because Tianjin has struggled with measles control in the context of China's larger elimination efforts, despite near universal immunization coverage among young children [25,26] and the completion of 2 major supplementary immunization activities in the past 10 years, which have each targeted hundreds of thousands of children for vaccination [27]. With administration of the initial measles dose at 8 months of age, China's immunization program attempts to strike a balance between immunizing at earlier ages to provide protection to these infants, who form an increasing proportion of all case patients, and the poorer immune response elicited at earlier ages [15].…”

Trends of vaccine-preventable diseases in Afghanistan from the Disease Early Warning System, 2009–2015

“…Data from 2012 were not available, but we did find significantly lower rates of measles in 2013 and 2014 compared to 2009. However, the resurgence in cases in 2015 points to the difficulty and the necessity of maintaining a cohort that is fully immunized against this highly infectious disease: a study of measles in Tianjin, China, also found that rates of disease bounced back within 2 to 4 years of an SIA [ 30 ]. The coverage of the second dose of measles vaccine in Afghanistan is only estimated to be around 60% as of 2015 [ 25 ].…”