Measles – The epidemiology of elimination

Abstract

Tremendous progress has been made globally to reduce the contribution of measles to the burden of childhood deaths and measles cases have dramatically decreased with increased two dose measles-containing vaccine coverage. As a result the Global Vaccine Action Plan, endorsed by the World Health Assembly, has targeted measles elimination in at least five of the six World Health Organisation Regions by 2020. This is an ambitious goal, since measles control requires the highest immunisation coverage of any vaccine preventable disease, which means that the health system must be able to reach every community. Further, while measles remains endemic in any country, importations will result in local transmission and outbreaks in countries and Regions that have interrupted local endemic measles circulation. One of the lines of evidence that countries and Regions must address to confirm measles elimination is a detailed description of measles epidemiology over an extended period. This information is incredibly valuable as predictable epidemiological patterns emerge as measles elimination is approached and achieved. These critical features, including the source, size and duration of outbreaks, the seasonality and age-distribution of cases, genotyping pointers and effective reproduction rate estimates, are discussed with illustrative examples from the Region of the Americas, which eliminated measles in 2002, and the Western Pacific Region, which has established a Regional Verification Commission to review progress towards elimination in all member countries.

Public health responses during measles outbreaks in elimination settings: Strategies and challenges

“…It is thus essential to interrogate every outbreak and patterns of outbreaks, so as to pinpoint communities with geographical or shared socio-cultural features that are consistently missing out on the benefits of measles vaccination, or to identify settings allowing a greater opportunity for measles transmission. 111 Targeting vaccination strategies to fill these immunity gaps can be a valuable legacy of thorough outbreak investigations.…”

Measles occurrence, vaccination coverages and malnutrition in India: correlations, trends, and projections by time series analysis

“…1,[6][7][8][9][10][11][12] Measles outbreak size and duration depend on transmissibility which in turn is decided by susceptibility in the population due to non-immune status, frequency of contacts in the population and also the agent factors such as replication speed. 1,13 Basic reproduction number (R 0 ) is estimated for measles to be around 12-18, which is a measure of secondary cases generated from each primary case in a completely susceptible population. The effective reproduction number (R e ) is dependent on the proportion of susceptible individuals in the population.…”

“…There are many methods to estimate R e when appropriate data is available on epidemic curves and outbreak size, duration, distribution etc. [13][14][15] Vaccine efficacy depends on the age of vaccination and other epidemiological contexts. Some studies have shown that the efficacy of measles vaccine administered at 9-11 months of age is of the order of 85-90% in the Indian context.…”

The epidemiological and serological characteristics of measles in Dongguan, China, 2005–2014

“…4 Brazil and Canada also experienced large outbreaks in the same year. [4][5][6] China introduced measles vaccine in 1967. Measles vaccine (MV) is included in the Chinese National Expanded Program on Immunization (CNEPI) and is offered to all eligible children for free.…”