Professor Sheng Li co-authors “Demographic transition and the dynamics of measles in six provinces in China: A modeling study,” which was published in PLoS Medicine, April 4th, 2017. This collaborative systems modeling project was done by Professor Li and his colleagues from WHO, US CDC, China CDC and PSU.
Measles is a highly contagious childhood viral disease. Decades of increasing vaccination and development have led to dramatic declines in the global burden of measles, but the virus remains persistent in much of the world and is still an important cause of death among young children in developing countries. Significant measles resurgence was observed in past few years in Europe and North America, with NYC as a disease hotspot. Under the WHO’s Global Vaccine Action Plan, measles is targeted for elimination by 2020, but achieving global elimination remains a significant public health challenge. Understanding measles’ long term dynamic patterns and the underlying driven principles, evaluating existing public health interventions are particularly important to help inform global eradication.
As the most populous nation, China has a complete and updated measles surveillance system, which provides a unique opportunity for measles study. Although there have been significant improvements in measles’ vaccination and other inventions in the past few decades, China recently has observed a dramatic increase in measles cases among adults and infants, along with a decrease in the traditionally high risk child age groups. The measles vaccination intervention assessments were limited due to the unavailability of vaccine usage and wastage data.
Based on 50 years of measles surveillance data from 6 provinces in China, Professor Li and colleagues developed a novel catalytic model to explore the disease pattern and estimate public health intervention. This new approach overcomes the issue of unavailability and inconsistence of vaccine data. The research shows that a combination of demographic transition, as a result of declining birth rates, and reduced prevalence, due to improved vaccination, has shifted the age distribution of susceptibility to measles throughout China. The force of infection of measles has declined dramatically in the industrialized eastern provinces in the last decade, driving a concomitant increase in adult cases while central and western provinces exhibit dynamics consistent with endemic persistence. The shift in the age distribution of susceptibility emphasizes the importance of progressive control strategies and measures to evaluate program success that anticipate this transition in observed incidence.
In summary, Professor Li says, “This result adds an important evidence for planning measles eradication locally. This project is an interesting example how systems modelers can step out of the traditional theoretical modeling zone, and work with field epidemiologists to solve important public health problems by developing novel systems models.”