Measles and the canonical path to elimination
By Matthew Graham, Amy K. Winter, Matthew Ferrari, Bryan Grenfell, William J. Moss, Andrew S. Azman, C. Jessica E. Metcalf, Justin Lessler
Science10 May 2019 : 584-587 Open Access
As birth rates change over time and vaccine coverage improves, measles dynamics change in a globally consistent way.
The path to elimination
Measles is highly infectious and can be dangerous. The classic 1968 vaccine is highly effective, and it should be possible to eliminate measles. Graham et al. found that measles transmission changes as vaccination coverage and birth rates (that is, the rate of arrival of susceptible individuals into the population) change in a country in response to socioeconomic variables. As a result, measles everywhere follows the canonical mode of decline in response to vaccination campaigns. Incidence is initially high, and variability is low. As incidence declines, variability increases, and as incidence drops toward elimination, so does variability. It is possible to identify countries that are deviating from this expectation and to adapt their vaccination programs to regain the path to elimination.
Science, this issue p. 584
All World Health Organization regions have set measles elimination goals. We find that as countries progress toward these goals, they undergo predictable changes in the size and frequency of measles outbreaks. A country’s position on this “canonical path” is driven by both measles control activities and demographic factors, which combine to change the effective size of the measles-susceptible population, thereby driving the country through theoretically established dynamic regimes. Further, position on the path to elimination provides critical information for guiding vaccination efforts, such as the age profile of susceptibility, that could only otherwise be obtained through costly field studies or sophisticated analysis. Equipped with this information, countries can gain insight into their current and future measles epidemiology and select appropriate strategies to more quickly achieve elimination goals.