TOP 10 Countries by Vaccine-Preventable Disease Outbreaks per Million (2015–2025)
Vaccine-preventable diseases (VPDs) such as measles, diphtheria, pertussis, meningococcal meningitis and polio remain powerful stress-tests for national immunisation systems. Even after two decades of progress, measles alone has repeatedly surged, with large and disruptive outbreaks concentrated in a relatively small group of countries.
This StatRanker snapshot focuses on countries that experienced the highest measles and other VPD outbreaks per million population between 2015 and 2025, using measles incidence as the primary tracer (supplemented by other VPD signals such as meningitis and polio flare-ups). The metric is based on peak cumulative outbreak incidence per million in major outbreak years, not on a smooth long-run average.
Peak values are rounded approximations based on WHO/UNICEF surveillance and published outbreak investigations. They reflect cumulative measles cases per million population in major outbreak years within 2015–2025, and are intended for comparative, not clinical, use.
| Rank | Country | Peak measles incidence per 1M (2015–2025, approx.) |
|---|---|---|
| 1 | Samoa | ≈ 28 000 |
| 2 | Madagascar | ≈ 5 600 |
| 3 | Democratic Republic of the Congo | ≈ 3 900 |
| 4 | Ukraine | ≈ 2 600 |
| 5 | Romania | ≈ 1 600 |
| 6 | Kazakhstan | ≈ 1 500 |
| 7 | Ethiopia | ≈ 650 |
| 8 | Philippines | ≈ 440 |
| 9 | Nigeria | ≈ 140 |
| 10 | Pakistan | ≈ 75 |
Each bar shows approximate peak measles incidence per 1 million people during major outbreak years (2015–2025). Values are harmonised from WHO/UNICEF measles surveillance and outbreak reports and rounded for clarity.
How immunisation coverage shapes vaccine-preventable disease outbreaks
The countries at the top of the outbreaks-per-million ranking are not necessarily those with the weakest health systems overall. Instead, they tend to share specific coverage gaps in routine immunisation and booster campaigns, often layered on top of conflict, migration or local pockets of vaccine hesitancy.
WHO/UNICEF coverage estimates show that global DTP3 coverage recovered to roughly the mid-80% range in 2022, but still left tens of millions of children under- or un-vaccinated each year. In many of the countries in Table 1, MCV1 (first measles-containing vaccine) coverage has periodically dropped far below the 95% herd-immunity threshold, creating reservoirs of susceptibility that later show up as sharp outbreaks.
Bands summarise typical DTP3 (three-dose diphtheria–tetanus–pertussis) and MCV1 (first measles-containing vaccine) coverage over 2015–2022 using WHO/UNICEF estimates and published outbreak reports. Values are indicative, not official country statistics.
| Country | DTP3 coverage band, 2015–2022 | MCV1 coverage band, 2015–2022 |
|---|---|---|
| Samoa | Typically high (>85%) before 2017; short-lived disruption around 2018 with rapid catch-up after 2019 emergency campaign. | Fell from ~70–75% to ~30–40% before the 2019 outbreak, then pushed back above 90% after mass vaccination. |
| Madagascar | Mostly in the 60–75% band, with large regional gaps and recurring “zero-dose” clusters. | Around 60–70% nationally during the 2018–2019 epidemic; much lower in remote districts. |
| DR Congo | Generally ~55–70% with pronounced subnational inequity, especially in conflict-affected provinces. | ~55–65% in many years, leaving millions of children susceptible ahead of the 2019–2020 mega-outbreak. |
| Ukraine | Wide swings: some years near 90%, others well below 80% due to supply and trust crises in the 2010s. | Often in the 80–90% band overall, but with deep cohort gaps that set the stage for the 2017–2019 measles epidemic. |
| Philippines | Typically 70–85%, with setbacks linked to vaccine scares and local programme disruptions. | Declined from near-universal coverage to roughly the mid-70% range ahead of the 2019 outbreak. |
| Nigeria | Frequently around 55–65% nationally, lower in insecure northern states and informal settlements. | ~55–65% with sharp north–south and urban–rural gradients. |
| Pakistan | Often reported around 75–85% overall; however, hard-to-reach districts and conflict areas lag well behind. | Roughly 75–85% nationally, but with persistent pockets of under-immunisation despite repeated campaigns. |
| Romania | Traditionally high (>90%), but challenged by vaccine hesitancy in some communities. | Dropped below 90% in multiple years, far short of the 95% needed for sustained measles elimination. |
| Kazakhstan | Often close to or above 90%, with strong national programmes but emerging local gaps. | High on average (near the upper-80s/low-90s), yet still leaving under-vaccinated pockets that fuelled the 2024 surge. |
| Ethiopia | Generally 60–75%, with coverage shocks linked to conflict, displacement and funding interruptions. | Around 60–70% in recent years, with heavy clustering of unvaccinated children in crisis-affected regions. |
Each dot represents one of the TOP 10 countries, plotting an approximate peak measles incidence per 1 million (vertical axis) against an indicative MCV1 coverage level in the years preceding major outbreaks. Lower coverage values line up with much higher observed incidence.
Interpreting “outbreaks per million” — limits and policy signals
This ranking is intentionally focused on per-capita outbreak burden, not on the absolute number of cases. As a result, small and very small countries like Samoa or island states with temporary collapses in vaccine coverage rise to the top because even a few thousand cases translate into extremely high incidence per million. Larger countries such as the DRC, Pakistan or Nigeria contribute a substantial share of global measles and other VPD cases, but their incidence per million is “diluted” by population size.
Second, the metric is anchored in measles surveillance because measles data are the most complete, timely and comparable across countries. Other vaccine-preventable threats — meningococcal meningitis, diphtheria, pertussis, polio — are incorporated qualitatively through country case studies and WHO situation reports rather than as separate numerical series.
Health-system patterns across the TOP 10
Despite their diversity, the outbreak-heavy countries exhibit a recurring pattern: children in specific geographies, social groups or birth cohorts repeatedly miss routine doses. In the DRC, Ethiopia, Nigeria and Pakistan, conflict, displacement and geography make it hard to reach remote or insecure communities even when vaccines are available. In Ukraine, Romania and Kazakhstan, political crises, misinformation and pockets of hesitancy have eroded confidence in the MMR vaccine, producing deep immunity gaps that later ignite regional outbreaks.
Small island states such as Samoa highlight a different vulnerability: short but severe programme failures. A rapid fall in measles coverage to around one third of infants preceded the 2019 epidemic; once trust and programme capacity were restored, a nationwide emergency campaign quickly pushed coverage back above 90% and the outbreak was controlled. That experience underscores how much difference swift, well-communicated corrective action can make even after a major failure.
Implications for policy and monitoring
For ministries of health and partners, an “outbreaks per million” perspective is a useful complement to global averages. It highlights:
• Where zero-dose and under-immunised children cluster, especially in conflict-affected or
marginalised regions.
• How quickly coverage shocks translate into real outbreaks — usually within 2–5 years for
measles — and therefore how urgent remedial action must be.
• Which countries may need combined strategies: routine strengthening, periodic catch-up,
targeting of misinformation, and cross-border coordination, particularly where large migrant or displaced
populations are involved.
From a monitoring perspective, routinely plotting MCV1 and DTP3 coverage against outbreak incidence (as in Figures 1–2) helps identify where “silent risk” is accumulating before a crisis appears in hospital wards. Integrating these indicators into national dashboards, joint appraisals and global initiatives like the Immunization Agenda 2030 can keep attention on the countries most likely to generate the next major VPD emergencies.
- WHO / UNICEF Immunization Data Portal – global country-level time series on measles and other vaccine-preventable disease cases, as well as DTP3 and MCV1 coverage estimates (WUENIC). immunizationdata.who.int
- Measles mega-outbreaks in DRC, Madagascar and other high-burden countries – UNICEF and WHO situation reports and case studies documenting hundreds of thousands of measles cases and thousands of deaths in the 2018–2020 period. UNICEF DRC measles briefing · Madagascar measles outbreak analysis
- Samoa and Pacific island measles epidemics – peer-reviewed and agency reports describing the 2019 Samoa outbreak, with more than 5,600 cases and over 80 deaths in a population of around 200,000, and very low pre-outbreak measles coverage. Lancet Pacific measles commentary
- Ukraine and European Region measles resurgence – analyses of Ukraine’s 2017–2019 measles epidemic and WHO/UNICEF updates on the record number of measles cases in the European Region in 2024, particularly in Romania and Kazakhstan. Ukraine measles and war · UNICEF / WHO Europe measles 2024
- High-burden VPD countries including Nigeria, Pakistan, Ethiopia – WHO, UNICEF, Gavi and national-level outbreak investigations covering measles and other VPD cases, immunisation gaps and large-scale catch-up campaigns in the 2015–2025 period. MMWR routine vaccination coverage reports · Pakistan measles-rubella campaigns
