Measles

Key takeaways

• MMR vaccine doses: 2 doses: at 12 to 15 months and at 4 to 6 years
• Protection: about 97% after 2 doses and 93% after 1 dose
• Most useful single change: Check your family's vaccination records; adults born in 1957 or later without evidence of immunity need at least 1 dose.
• Commonest mistake: Walking into a clinic or ER unannounced with a fever and rash; call ahead so staff can protect other patients.
• See a doctor if any of the signs under "When to get help" below apply to you.

Why it matters

Measles can lead to pneumonia, brain swelling and death, especially in young children, and outbreaks in the US are linked to pockets of people who are not vaccinated.

The numbers, in one place

Published figures for Measles

Measure	Figure
MMR vaccine doses	2 doses: at 12 to 15 months and at 4 to 6 years
Protection	about 97% after 2 doses and 93% after 1 dose
How contagious	up to 9 in 10 unprotected close contacts will catch it
Contagious period	from 4 days before to 4 days after the rash appears
Virus in the air	can linger for up to 2 hours after an infected person leaves a room
Babies 6 to 11 months traveling internationally	1 early dose before travel, then the usual 2 doses later

What helps

• Check your family's vaccination records; adults born in 1957 or later without evidence of immunity need at least 1 dose
• Ask your doctor about MMR before any international travel
• If you were exposed and are not immune, call your doctor quickly; a vaccine within 72 hours or immune globulin within 6 days can help
• Stay home and away from others, including school and work, until your health department says you can return

What to avoid

• Walking into a clinic or ER unannounced with a fever and rash; call ahead so staff can protect other patients
• Assuming vitamin A or other supplements replace vaccination
• Delaying a child's scheduled MMR doses

In depth

Measles virus enters through the nose, mouth or eyes and first multiplies in the airways before spreading through the bloodstream. Symptoms usually begin about a week or two after exposure with high fever, cough, runny nose and red, watery eyes. A few days later, tiny white spots may appear inside the mouth, and then a red, blotchy rash starts on the face and spreads downward.

Measles also weakens the immune system in a way that can last for months or years after recovery. The virus destroys a portion of the body's memory immune cells, erasing some protection against other infections. This immune damage helps explain why measles is linked to pneumonia and other infections well after the rash has faded.

The MMR vaccine is highly effective, and measles was declared eliminated in the US in 2000, meaning it no longer spreads year-round. However, travelers bring it back from countries where it is common, and outbreaks can spread quickly in communities where many people are unvaccinated. Keeping vaccination rates high protects babies and others who cannot be vaccinated.

Signs and symptoms

• High fever, which can exceed 104°F (40°C)
• Cough, runny nose and red, watery eyes in the days before the rash
• Tiny white spots inside the cheeks, called Koplik spots
• A red, flat rash that starts at the hairline and spreads down the body
• Diarrhea, ear pain or trouble breathing, which can signal complications
• Unusual sleepiness, confusion or seizures, which need emergency care

Causes and risk factors

• Not being vaccinated, or having only one dose
• International travel to areas with measles outbreaks
• Being in a community with low vaccination rates
• Infants too young for the routine MMR schedule
• Weakened immune systems that cannot receive live vaccines
• Vitamin A deficiency, which is linked to more severe illness

How it is checked

Measles is diagnosed with a combination of symptoms, exposure history and lab tests. Testing usually involves a throat or nose swab for the virus's genetic material (PCR) and a blood test for antibodies. Doctors report suspected cases to the health department right away so contacts can be traced and protected.

Calling ahead before visiting a clinic is important. Staff can arrange for you to enter through a separate door, wear a mask and be placed in a room where the virus will not spread to others, since measles can linger in the air of a waiting room.

Related topics

• Childhood Vaccinations: Sorting the Evidence From the Noise (Children's Health)
• The Evidence on How Vaccines Work, Without the Hype (Vaccinations)
• Vaccination: What the Evidence Actually Says (Immunity)
• The Evidence on Pneumonia, Without the Hype (Respiratory Health)

Where to go next

• Measles in Five Minutes
• Measles: What the Evidence Actually Says
• Infectious Diseases: The Complete Guide
• Lyme Disease and Ticks: What Published Guidance Supports
• The Evidence on West Nile Virus and Mosquitoes, Without the Hype

When to get help

Call your doctor right away, before visiting, if you or your child has a fever with a rash or has been exposed to measles. Call 911 for trouble breathing, a seizure, severe drowsiness or confusion, or a baby who is limp or not feeding.

Where this comes from

• CDC — About Measles
• CDC — Measles Vaccination

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.