Measles is Highly Contagious: What Parents Should Know

We’ve all heard of measles, but many of us might not fully understand it. In recent years, cases have surged in areas where vaccination rates have declined. Just this past week, an unvaccinated child died in Texas, marking the first measles-related death in a decade.

Pediatric infectious disease expert Ian C. Michelow, MD, addresses how measles spreads, the potential risks, and how to protect your family and the community.

What is measles?

Measles is a highly contagious viral infection—that means antibiotics won’t work against it. However, there is a highly effective vaccine that can prevent the infection. The disease affects the respiratory system and spreads easily through talking, coughing and sneezing.

Many of us think of the hallmark red measles rash. Beyond the rash, the infection can lead to severe complications, especially in young children and those who are immunocompromised.

Symptoms of measles

Measles symptoms show up 7 to 14 days after exposure and include:

High fever
Cough
Runny nose
Red, watery eyes
White spots inside the mouth (Koplik spots)
A red, blotchy rash that starts on the face and spreads downward

Many children do recover from measles without any issues, but the disease can be severe and life-threatening in some cases.

How contagious is measles?

Extremely contagious—far more so than the flu or COVID-19. The virus spreads through tiny droplets suspended in the air when an infected person coughs or sneezes.

>>Fact: Measles droplets stay suspended in the air for up to two hours after the infected person leaves the room. One contagious person can infect 12 to 18 people.

The only way to prevent measles outbreaks is through widespread vaccination. For kids, two doses of the measles, mumps, and rubella (MMR) vaccine has been a lifesaver since the 1960s at a 97% efficacy rate.

Vaccination against measles is crucial

Vaccination is the safest and most effective way to prevent measles. The measles vaccine is usually given as part of the measles, mumps, and rubella (MMR) vaccine. It may also be given together with the chicken pox (varicella) vaccine.

When should babies and kids get the MMR vaccine?

The Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend:

First dose: 12 to 15 months of age
Second dose: 4 to 6 years of age

How effective is the MMR vaccine?

Highly effective:

• One dose is about 93% effective.
• Two doses are about 97% effective.

This means that nearly all children who get both doses will have lifetime protection from measles. In the rare case that a vaccinated person becomes infected with measles, the illness is usually much milder and uncomplicated.

What happens if a child is not vaccinated against measles?

Choosing not to vaccinate puts children at risk of severe complications from measles, which can include:

Pneumonia: The most common cause of measles-related death in young kids.
Encephalitis: A dangerous swelling of the brain that can be fatal.
Dehydration and malnutrition: From severe diarrhea and difficulty eating or drinking.
Hearing loss or blindness: Measles can cause long-term complications affecting vision and hearing.

Beyond individual health risks, unvaccinated individuals contribute to the spread of measles, endangering babies too young to be vaccinated, pregnant women, and people with weakened immune systems.

Is the MMR vaccine safe?

The MMR vaccine is safe for most children. Side effects, if they occur, are usually mild, such as a sore arm or low-grade fever. Severe reactions are extremely rare. A harmless red rash may develop after the vaccine.

What is the role of herd immunity in preventing measles?

When most of the population is vaccinated (at least 95%), measles is much less likely to spread. This concept is known as herd immunity, and it protects those who cannot be vaccinated (newborns or those with medical conditions) or the small percentage of people who do not respond to the vaccine. However, if vaccination rates drop, outbreaks can occur quickly, as seen in recent years.

Together, we can keep measles under control and protect future generations from this highly contagious disease.

Ian C. Michelow, MD, FCPaed

Dr. Michelow is division head of Infectious Diseases and Immunology at Connecticut Children’s and professor of pediatrics at the University of Connecticut School of Medicine. His experience and interests span clinical, basic science and translational research topics with an emphasis on mechanisms of infection across microbial kingdoms, host-pathogen interactions and immune-mediated interventions. His research activities have included the study of malaria pathogenesis and vaccines, Ebola virus disease, clinical epidemiology and biomarkers of bacterial and viral infections in children including COVID-19, congenital syphilis, pediatric osteoarticular, pulmonary and intracranial infections, among others. He has also contributed to medical education by mentoring students on emerging infectious diseases research projects under an NIH-sponsored grant, developing new models for clinical teaching, and participating in the ACGME Milestones 2.0 development for pediatric infectious diseases competency-based education.