Measles Incidence by Country, 2015–2025: Highest Annual Rates
Measles Incidence by Country: Highest Annual Rates, 2015–2025
Samoa recorded the highest annual measles incidence among sovereign countries in the available WHO data for 2015–2025, reaching 27,109.4 reported cases per million people in 2019. Mongolia ranks second with a 2016 peak of 9,955.6 per million, followed by Madagascar at 7,556.1 in 2019.
The ranking uses annual measles incidence published by the WHO Immunization Data Portal. The figures are based on confirmed cases reported by national authorities through the WHO/UNICEF Joint Reporting Form on Immunization and related official reporting channels. Higher incidence ranks higher.
The 2025 column is included in the current WHO export. Some country and area entries remain blank for 2025, so missing observations are left missing rather than treated as zero. Among available 2025 values, Mongolia recorded the highest rate at 3,936.8 per million, below its own 2016 peak and not enough to change the Top 10.
All 10 entries are official reported values. The ranking contains no forecasts and no modeled projections. Each country's value is its highest observed annual measles incidence within the 2015–2025 reporting window.
Samoa · 2019 · reported measles cases per 1 million population.
Somalia · 2017 · tenth-highest confirmed country peak.
Sovereign countries with the highest confirmed annual rates in the current WHO data.
10 official values · 0 official forecasts · 0 modeled projections.
Reported measles cases per 1 million population · current WHO export checked August 20, 2026.
What measles incidence per million shows
Incidence expresses reported measles cases relative to population. Using a rate instead of an absolute case count makes it easier to compare countries of very different sizes. A large country can report many cases but still have a lower incidence rate than a small country in which a substantial share of the population is affected.
This page uses each country's highest annual rate between 2015 and 2025. It therefore captures the most intense reported year rather than the total burden accumulated across the full eleven-year period. A country with one exceptionally severe year can rank above a country that experienced lower but more persistent transmission.
The distinction is especially important for small populations. Samoa and Tonga reached very high per-capita rates in 2019 even though their absolute case totals were much smaller than those of some large countries. Per-million incidence describes population exposure to reported disease more directly than a simple case total.
Incidence is not an outbreak count. WHO does not publish a harmonized country ranking of all vaccine-preventable disease outbreaks for 2015–2025 using one common outbreak definition. Measles incidence is used here because WHO provides a comparable annual country-level measure.
These figures still need careful interpretation. WHO displays surveillance data reported by national authorities, and reporting quality can vary. A lower recorded rate does not necessarily mean that every infection was detected or that surveillance systems were equally sensitive across countries.
Countries with the highest annual measles incidence
Samoa stands well above the rest of the ranking. Its 2019 rate was about 2.72 times Mongolia's second-place peak and roughly 3.59 times Madagascar's third-place value.
Five highest country peaks in the WHO series, 2015–2025
| Rank | Entity | Value | Region / note |
|---|---|---|---|
| 1 | Samoa | 27,109.4 | Western Pacific · official value · WHO/UNICEF JRF · 2019 peak. |
| 2 | Mongolia | 9,955.6 | Western Pacific · official value · WHO/UNICEF JRF · 2016 peak. |
| 3 | Madagascar | 7,556.1 | Africa · official value · WHO/UNICEF JRF · 2019 peak. |
| 4 | Tonga | 6,236.4 | Western Pacific · official value · WHO/UNICEF JRF · 2019 peak. |
| 5 | Democratic Republic of the Congo | 3,582.9 | Africa · official value · WHO/UNICEF JRF · 2019 peak. |
Values are reported cases per 1,000,000 total population. The ranking uses the numerical WHO incidence value before display formatting.
Top 10 peak annual measles incidence rates
The distribution is steep. Samoa is the clear outlier, while the gap narrows considerably from fifth place onward.
Methodology
The numerical source is the WHO Immunization Data incidence-rate export available on August 20, 2026. The file contains annual country and area observations for selected vaccine-preventable diseases, including measles data through 2025.
Metric
Highest observed annual reported measles incidence for each sovereign country between 2015 and 2025.
Unit
Reported confirmed measles cases per 1,000,000 total population.
Direction
Descending. A higher annual incidence rate produces a higher rank.
Data status
Country-reported official values. No forecasts, interpolation or modeled projections are included.
Calculation
For every country, annual measles incidence observations from 2015 through 2025 were compared and the largest available value was retained. The countries were then sorted from highest to lowest peak incidence.
Formula: reported confirmed measles cases ÷ total population × 1,000,000. WHO identifies United Nations World Population Prospects 2024 as the population source used for the incidence-rate denominator.
2025 data check
The current WHO export contains 2025 incidence observations. Mongolia has the highest available 2025 measles incidence at 3,936.8 per million, but this remains below Mongolia's own 2016 peak of 9,955.6. No available 2025 observation creates a new country entry in the Top 10.
Some 2025 country and area cells are still blank because WHO updates country data as reports are received. Blank observations are not converted to zero and are not estimated. The table therefore ranks the highest values actually reported in the current WHO dataset.
Country coverage
The WHO export includes sovereign states as well as some territories and other country-area entries. This ranking is limited to sovereign countries. Tokelau, which would otherwise appear among the highest area-level rates, is therefore excluded.
Source hierarchy
The WHO incidence-rate export is used for every numerical value and rank. WHO pages describing the JRF reporting process and vaccine-preventable disease surveillance standards are used only for definitions and reporting context. No commercial or secondary ranking source is used to change WHO values.
Missing values and conflicts
Missing country-years remain missing. They are not treated as zero, interpolated or replaced with a neighboring year's value. If another presentation of the same indicator differs from the current WHO export, the current WHO export takes priority; conflicting values are not averaged.
Rounding and assumptions
Rates are displayed to one decimal place, matching the precision of the WHO incidence export. No adjustment is made for surveillance sensitivity, underreporting, vaccination coverage, age structure or differences in health-system capacity.
What this metric does not measure
It does not measure the number of separate outbreaks, cumulative incidence across eleven years, deaths, hospitalizations, vaccine coverage, outbreak duration or the estimated number of infections that were never reported.
Top 10 countries by peak reported measles incidence
The peak years range from 2015 to 2024. This spread shows that the highest rates in the table did not come from one global epidemic year, although 2019 accounts for four of the ten entries.
Highest annual reported measles incidence per 1 million population, available WHO data for 2015–2025
| Rank | Entity | Value | Region / note |
|---|---|---|---|
| 1 | Samoa | 27,109.4 | Western Pacific · official value · WHO/UNICEF JRF · 2019 peak. |
| 2 | Mongolia | 9,955.6 | Western Pacific · official value · WHO/UNICEF JRF · 2016 peak. |
| 3 | Madagascar | 7,556.1 | Africa · official value · WHO/UNICEF JRF · 2019 peak. |
| 4 | Tonga | 6,236.4 | Western Pacific · official value · WHO/UNICEF JRF · 2019 peak. |
| 5 | Democratic Republic of the Congo | 3,582.9 | Africa · official value · WHO/UNICEF JRF · 2019 peak. |
| 6 | Kyrgyzstan | 2,962.2 | Europe · official value · WHO/UNICEF JRF · 2015 peak. |
| 7 | Bosnia and Herzegovina | 2,514.7 | Europe · official value · WHO/UNICEF JRF · 2024 peak. |
| 8 | Azerbaijan | 1,797.9 | Europe · official value · WHO/UNICEF JRF · 2024 peak. |
| 9 | Liberia | 1,544.7 | Africa · official value · WHO/UNICEF JRF · 2022 peak. |
| 10 | Somalia | 1,544.5 | Eastern Mediterranean · official value · WHO/UNICEF JRF · 2017 peak. |
WHO's export also contains some territories and other area entries. Only sovereign countries are ranked here. Missing annual observations are excluded rather than treated as zero.
What stands out in the Top 10
Key Insight
Samoa's 2019 rate of 27,109.4 per million is about 2.72 times Mongolia's second-ranked peak and more than 17 times the tenth-place rate.
Notable Pattern
Four countries reached their maximum in 2019: Samoa, Madagascar, Tonga and the Democratic Republic of the Congo. No other peak year appears more than twice.
Regional Concentration
The Western Pacific, African and European WHO regions each account for three countries in the Top 10. Somalia is the only Eastern Mediterranean entry.
Outlier
Samoa's lead illustrates how sharply a per-capita disease rate can rise in a small population when reported cases increase quickly. Its separation from the rest of the table is unusually large.
How to interpret the results
A high position means that a country experienced at least one year with very high reported measles incidence relative to its population. It does not mean that the country had the highest incidence throughout the entire 2015–2025 period.
Peak incidence and cumulative burden answer different questions. Samoa's first-place position is driven by its exceptional 2019 rate. A country with moderate incidence across several years could accumulate substantial disease burden without matching that single-year peak.
Population size also matters. Per-million rates improve comparison between large and small countries, but small populations can produce highly volatile rates. Absolute case totals should therefore be consulted when the scale of the public-health response is the main question.
Surveillance quality remains an important limitation. The WHO series is based on reported cases, so differences in case detection, reporting completeness and national surveillance systems can affect international comparisons.
The results should also remain separate from outbreak statistics. An outbreak is an epidemiological event defined according to disease-specific criteria. Annual incidence is a population rate. Combining the two as if they were the same measure would produce a misleading country comparison.
FAQ
Which country had the highest reported measles incidence between 2015 and 2025?
Samoa ranks first in the available WHO data, with 27,109.4 reported cases per million population in 2019.
Is this a ranking of measles outbreaks?
No. The values are annual measles incidence rates. They do not count the number of separate outbreak events.
Why does the ranking focus on measles instead of all vaccine-preventable diseases?
WHO publishes comparable annual country-level measles incidence, while there is no single harmonized country series counting all vaccine-preventable disease outbreaks under one common definition for the full 2015–2025 period.
Are 2025 data included?
Yes. The current WHO incidence export includes 2025 observations. Mongolia has the highest available 2025 rate at 3,936.8 per million, but its 2016 rate remains higher and no available 2025 value changes the Top 10.
What happens when a 2025 value is missing?
A blank WHO observation remains missing. It is not converted to zero and no estimate is inserted.
How is measles incidence per million calculated?
Reported confirmed measles cases are divided by total population and multiplied by 1,000,000.
Why is Tokelau not included even though WHO reports an incidence value?
The WHO export contains territories and other area entries as well as sovereign states. This page ranks sovereign countries only, so Tokelau is excluded.
Are any figures forecasts or modeled estimates?
No. All ten ranking values are official country-reported observations published through the WHO Immunization Data system.
Sources
WHO Immunization Data Portal
Primary source environment for country-level vaccine-preventable disease incidence and reported-case data.
WHO Incidence Rate Data Export
Numerical source used for the annual measles incidence values and the 2015–2025 country comparison.
https://srhdpeuwpubsa-geecgzbpd5h0fueu.z01.azurefd.net/whdh/WIISE/export/incidence-rate-data.xlsx
WHO/UNICEF Joint Reporting Process
Explains the annual country reporting system through which WHO and UNICEF collect immunization and vaccine-preventable disease data.
WHO Vaccine-Preventable Disease Surveillance Standards
WHO reference for disease-specific surveillance definitions and interpretation of reported vaccine-preventable disease data.
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