Measles and the Measles Vaccine

Intro

Measles is a highly contagious viral disease that can cause severe complications, including pneumonia, encephalitis, deafness, and death.
The measles vaccine — usually given as the combined MMR (measles, mumps, rubella) or MMRV (with varicella) — is one of the safest and most effective vaccines ever developed.

Thanks to immunisation, measles deaths have fallen dramatically, but outbreaks are returning wherever coverage drops.

Key Points

Contagious: Up to 90% of unvaccinated contacts will catch measles after exposure.
Herd immunity: ~95% coverage needed to stop outbreaks.
Vaccine effectiveness: ~97% after two doses.
Impact: Prevented an estimated 23 million deaths between 2000 and 2018.
Safety: Decades of surveillance confirm safety; no link to autism.

The Disease

Transmission: Spread via coughing, sneezing, or breathing; virus can linger in the air up to 2 hours.
Symptoms: High fever, cough, runny nose, red eyes, Koplik spots, and a spreading rash.
Complications: Pneumonia (most common cause of death), encephalitis (~1 in 1,000), SSPE (rare, fatal brain disorder years later).
At risk: Infants, pregnant women, and the immunocompromised.

The Vaccine

History: First licensed in 1963, improved versions soon followed.
Formulations: MMR or MMRV.
Effectiveness: One dose ~93%, two doses ~97%.
Safety: Common side effects are mild (fever, rash). Rare side effects include febrile seizures; serious reactions are extremely rare.
Myths: The 1998 autism claim was fraudulent and has been thoroughly debunked.

Global Recommendations

WHO: Two doses for all children, first at 9–12 months, second at 15–18 months.
CDC (US): First dose 12–15 months, second at 4–6 years.
ATAGI (Australia): 12 months (MMR), 18 months (MMRV). Catch-up for unvaccinated adults.

Recent Outbreaks

2025: Texas outbreak spread to nearby states after local vaccination rates dipped.
Europe and Asia continue to see resurgences linked to vaccine hesitancy and healthcare disruptions.
International travel remains a key driver of imported cases.

Risks / Benefits

Benefits: Prevents a disease with a case fatality rate of ~1–3 per 1,000 in high-income countries (higher in low-resource settings). Protects against severe complications and death.
Risks: Very small; overwhelmingly outweighed by benefits.

FAQ

Q: Is measles just a childhood rash?
A: No. It can cause life-threatening illness and long-term complications.

Q: Can adults get measles?
A: Yes. Adults without immunity remain at risk. Vaccination is recommended.

Q: How many doses are needed for lifelong protection?
A: Two doses usually provide lifelong immunity.

Q: Why do outbreaks still occur?
A: Measles is so contagious that even small drops in coverage allow outbreaks.