Abstract
Routine immunizations and supplementary immunization activities (SIAs) have significantly improved measles control over the past two decades in China. Progress towards eliminating measles currently faces multiple challenges as the infection age increases, and adult-targeted SIA strategies are being considered. This study developed an age-stratified susceptible-exposed-infectious-recovered model using a recently published contact matrix to depict measles transmissions between individuals in seven age groups. Hubei, a high measles-incidence province in central China, was the selected setting. The baseline scenario was calibrated by fitting with the 2012–2015 age-stratified incidence data. SIAs targeting multiple age groups were simulated. Adult-targeted (>29 years) two-year SIA cycles produced the greatest annual incidence rate decrease, reducing incidences by half over a long timespan with 90% coverage levels. Incidences could remain below 10/100,000 until 2030 if SIAs were provided to individuals ≥6 years old with at least 50% coverage. These findings will help officials prioritize supplementary vaccination strategies. Public health officials in China should consider adult-to-adult transmissions and provide adult-targeted SIAs. Although officials have reported approximately 90% SIA coverage in the past, SIAs for the adult population should be provided on shorter intervals, particularly for the aging population with decreased immunity.
Highlights
A result of the nation-wide SIAs in 2010, measles incidences dropped to a record low of 0.46 cases per 100,000 people in 2012; this was followed by a resurgence of incidences in 2013 and 2014 (2.04 and 3.88 cases per 100,000, respectively)[4,5], especially among unvaccinated young children nationally and adults over 15 years of age in certain localities[8]
These results indicate that two-dose immunization strategies are insufficient for controlling measles epidemics in the community due to the susceptible percentage growth each year
The strategy of supplementing routine immunizations with province-level SIAs has achieved a great success in reducing measles cases in China
Summary
A result of the nation-wide SIAs in 2010, measles incidences dropped to a record low of 0.46 cases per 100,000 people in 2012; this was followed by a resurgence of incidences in 2013 and 2014 (2.04 and 3.88 cases per 100,000, respectively)[4,5], especially among unvaccinated young children nationally and adults over 15 years of age in certain localities[8]. Most areas remain in an endemic state, with accumulating susceptible hosts and seasonal outbreaks experienced both regionally and nationally[4,9]. As the number of adult infections in China has increased, the aptitude of the current routine immunization strategy and supplemental SIAs for controlling future measles epidemics is in question.
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