Intro
“Measles elimination” is commonly misunderstood. It does not mean measles no longer exists. It means a country or region has stopped continuous local transmission — even though imported cases can still occur.
This distinction matters because it explains how measles can return after years of low case numbers, and why maintaining high vaccination coverage remains essential.
Key points
- Elimination means sustained local transmission has been interrupted in a country or region.
- Eradication means the virus no longer circulates anywhere in the world.
- Measles is extremely contagious, so elimination depends on consistently high immunity levels.
- Elimination status can be lost if transmission continues long enough within a country.
What measles elimination means
In public health, elimination refers to the absence of continuous, endemic measles transmission for a defined period (commonly 12 months) in a specific geographic area.
Elimination can be achieved and maintained even if a country still experiences occasional measles cases — as long as those cases do not lead to ongoing local spread.
Elimination vs eradication
These terms are not interchangeable:
- Elimination: The disease is controlled locally (no sustained spread), but imported cases can still happen.
- Eradication: The disease is gone globally (no natural circulation anywhere).
Measles has been eliminated in some settings, but it has not been eradicated globally.
Why elimination is fragile
Measles spreads through the air and is among the most contagious infections known. Preventing ongoing spread typically requires very high population immunity — often described as around 95% two-dose coverage in communities.
Elimination becomes more fragile when:
- vaccination coverage declines
- exemptions increase
- under-immunised clusters form
- imported cases reach susceptible groups
Importantly, elimination can be threatened even when national vaccination coverage looks “okay” on average — because outbreaks are driven by local pockets of susceptibility.
What it means to “lose” elimination status
A country may be considered at risk of losing elimination status if measles transmission continues for long enough to be considered sustained endemic spread, rather than a contained outbreak sparked by importation.
Loss of elimination status is not permanent. It signals that population protection has weakened, and that restoring high immunity levels (and controlling outbreaks quickly) becomes a public health priority.
Why this matters
Measles is not a mild childhood illness. Complications can include pneumonia, encephalitis, and rare long-term neurological consequences. The highest risks tend to fall on:
- infants too young to be vaccinated
- immunocompromised individuals
- pregnant people
Elimination is valuable because it reduces preventable illness, protects vulnerable groups, and limits outbreak-driven strain on health systems.
FAQ
Q: Can a country have measles elimination and still see measles cases?
A: Yes. Imported cases can occur without elimination being lost, as long as there is no sustained local transmission.
Q: How does a country regain elimination?
A: By interrupting sustained transmission and restoring high vaccination coverage, often alongside targeted outbreak control and catch-up vaccination.
Q: Why do outbreaks happen even with “high” national coverage?
A: Because outbreaks are driven by local susceptibility. Pockets of low coverage can sustain transmission even if national averages appear acceptable.
Further reading
- World Health Organization (WHO) — measles and immunization resources
- CDC — measles (cases, outbreaks, and vaccine information)
- ECDC — measles surveillance and outbreaks (Europe)