Cholera: In highly endemic countries, a threshold increase in the annual number of reported cases compared to the average annual incidence over the past 5 years. Or for countries that are endemic-epidemic, over 12,000 cases reported annually.

Ebola: >50 cases.

Measles: Incidence equal to or greater than 20 reported measles cases per million population over a period of 12 months. Incidence is calculated as Number of cases / population * 1,000,000. The number of cases are the official case numbers published through the WHO/UNICEF joint data collection process. Country population estimates used for the denominator are the official United Nations population estimates prepared by the Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, as reflected in the most recent revision of the UN Population Division’s World Population Prospects (WPP).

Meningococcus: A cumulative attack rate >100 suspected meningitis cases per 100,000 population within one year in a given population based on a definition used for the African meningitis belt. Each region will set its own definitions for epidemics/outbreaks and targets for reduction according to local epidemiology.

Polio - wild poliovirus (WPV): > 1 WPV from any source (e.g., cases, environmental surveillance, contacts, healthy children's samples) in a country per year AND confirmation of local circulation in accordance with the standard operating procedures for outbreak response.

Polio - circulating vaccine-derived poliovirus (cVDPV): > 1 cVDPV from any source (e.g., cases, environmental surveillance, contacts, healthy children's samples) in a country per year AND evidence of local circulation in accordance with the standard operating procedures for outbreak response.

Yellow fever: 5 cases in endemic areas. Or >1 cases in an area previously without yellow fever.

Step 1) Across all WHO Member States, calculate the number of large or disruptive vaccine-preventable disease outbreaks.

Large or disruptive VPD outbreaks are identified using data collected by the International Coordinating Group for Vaccine Provision, WHO Headquarters and WHO Regional Offices with technical assistance from VPD control, elimination, and eradication initiatives. For multi-country outbreaks, each country’s portion of the outbreak was assessed separately.

Currently, this indicator captures outbreaks of seven VPDs. This indicator may be revised to capture additional VPDs, especially as additional diseases become vaccine preventable.