Qué debe saber sobre el sarampión y la vacuna MMR

Measles was once eliminated in the U.S., but cases are now increasing. In early 2025, a measles outbreak was reported in Texas, with cases continuing to spread. Health officials have linked the outbreak to low vaccination rates, raising concerns about the potential for further spread.

Carla Garcia Carreno, M.D., Medical Director of Infection Prevention and Control at Children’s Medical Center Plano, shares what you need to know about the measles, how the vaccine works and ways to keep your child safe.

What is measles?

Measles is a viral infection that can cause a red, blotchy rash, fever, cough and a runny nose. Esta afección altamente contagiosa también puede provocar complicaciones graves e incluso potencialmente mortales, como neumonía y encefalitis.

What are the signs and symptoms of measles?

Measles symptoms typically appear 7 to 14 days after exposure (but can present up to 21 days after contact with someone with measles). Estos síntomas incluyen:

• Fiebre alta

• Tos

• Secreción nasal

• Red, watery eyes

• Koplik spots (small white spots inside the mouth surrounded by localized redness) which may appear before the rash

• A red rash that starts on the face and spreads to the rest of the body

"The rash typically appears after day three or so of the fever," Dr. Carreno says.

What are possible complications of measles?

Complications from measles can be severe, especially in young children, pregnant women and individuals with weakened immune systems. Serious complications include pneumonia, brain swelling (encephalitis), and, in rare cases, death.

A rare but fatal complication can be seen around 10 years after acute measles, the Subacute Sclerosing Panencephalitis (SSPE), which can occur in 4 to 11 of 100,000 cases. This fatal form of encephalitis can present with seizures, loss of neurologic functions, and has a 95% mortality rate.

Another complication is the blunting of the cellular immune response after measles. In other words, it weakens the immune system’s response to defend against certain infections.

¿Cómo se propaga el sarampión?

El sarampión se contrae cuando se entra en contacto con una persona que tiene el virus. Cuando una persona con la afección tose, estornuda o habla, esto puede propagar el virus a personas, al aire y a superficies cercanas. The virus can travel more than six feet and live for up to two hours in the air after an infected person leaves the room. According to the Centers for Disease Control and Prevention (CDC), if one person has measles, 90% of unvaccinated individuals in close contact will also contract the disease.

A person with measles can be contagious from four days before the onset of the rash until four days after the rash appears. This means individuals can spread the virus before they even realize they are sick, increasing the risk of transmission in communities with low vaccination rates.

Debido a que el sarampión puede prevenirse con la vacuna MMR (sarampión, paperas y rubéola), la mayoría de los niños ahora están protegidos de contraer el virus.

"However, as doctors, we're always aware that we could present with a case of measles in the community," Dr. Carreno says. "So, we always need to have the high index of suspicion if a patient presents with symptoms."

How are measles treated?

There is no specific antiviral treatment for measles. Management focuses on relieving symptoms and preventing complications. El tratamiento puede incluir lo siguiente:

• Rest and plenty of fluids

• Fever reducers such as acetaminophen (Tylenol) or ibuprofen (Advil)

• Vitamin A supplements, which have been shown to reduce measles severity in children (a deficiency in Vitamin A can be associated with a more severe course of the disease)

• Monitoring for complications, such as pneumonia or encephalitis, which require immediate medical attention

Contact your pediatrician if you suspect your child may have been exposed to measles.

¿Cómo actúa la vacuna contra el sarampión?

Cuando un virus o una bacteria ataca, el cuerpo crea anticuerpos para combatir la infección. Each antibody is specific to that infection. Una vez que el organismo ha producido estos anticuerpos, puede reconocer y combatir la infección en el futuro, incluso antes de que se muestren los síntomas.

Las vacunas son una forma segura de exponer el cuerpo al virus sin contraer la enfermedad. They allow the body to have a natural immunity to the condition without the risk of serious complications from the natural disease.

La vacuna MMR es una vacuna 3 en 1 que protege a su hijo contra el sarampión, las paperas y la rubéola. La inyección contiene cepas debilitadas de cada uno de estos virus. El sistema inmunitario del organismo reconoce los virus y crea anticuerpos para combatir las cepas debilitadas.

When should kids get the measles vaccine?

Children should receive two doses of the MMR vaccine at the following times:

• The first dose at 12 to 15 months of age

• The second dose at 4 to 6 years of age

The vaccine provides lifelong protection for most people.

¿Cómo protejo a un bebé demasiado pequeño como para recibir la vacuna?

Infants under 12 months are too young to receive the MMR vaccine, so it is important to:

• Ensure all family members and caregivers are vaccinated

• Avoid exposing infants to crowded areas where measles may spread

• Keep babies away from individuals who are sick or unvaccinated

Be sure to talk to your pediatrician about a recommended vaccine schedule if your baby is under 12 months and will be traveling with you to an endemic area, a country with measles circulation or in case of a local outbreak of measles.

Similarly, if your child or any other person in the household cannot receive the vaccine because of a weakened immune system, protecting those surrounding the vulnerable person is essential.

Should adults get a measles booster shot?

La mayoría de los adultos que han recibido una vacuna contra el sarampión no requieren vacuna de refuerzo. Los adultos que fueron vacunados entre 1963 a 1967 pueden considerar recibir un refuerzo, ya que la vacuna durante esos años no fue tan eficaz como la vacuna actual. Adults who are unsure of their vaccination status should talk to their doctor about getting a blood test or an additional dose of the MMR vaccine.

¿Hay efectos secundarios de la vacuna contra el sarampión?

La mayoría de los niños no experimentan ningún efecto secundario de la vacuna MMR. Los efectos secundarios más frecuentes suelen ser leves y pueden incluir sarpullido, fiebre o dolor temporal. A algunos padres les preocupa que la vacuna MMR esté relacionada con el autismo. However, there is no scientific evidence that supports that claim.

¿Puede contraer sarampión si ha sido vacunado?

Si el niño recibió la vacuna MMR, no debe contraer la enfermedad si entra en contacto con una persona que tiene sarampión. In rare cases, about 3% of vaccinated individuals may still be at risk of infection, though their symptoms tend to be milder. Además, los niños pequeños que no han recibido su segunda dosis de la vacuna MMR tienen un mayor riesgo de contraer la enfermedad.

A medida que la vacuna MMR se vuelve más frecuente en todo el mundo, las tasas de sarampión han disminuido en todo el mundo, lo que hace que sea menos probable que se exponga a una persona con el sarampión. Vacunar al niño contra el sarampión puede ayudar a garantizar que su familia y su comunidad estén protegidas contra la enfermedad.

Vacúnese

​The best way to prevent measles and its complications is through vaccination. If you are unsure whether your child is up to date on their MMR vaccine, contact your pediatrician today.

Obtenga más información sobre las vacunas y cómo pueden proteger al niño de enfermedades graves.