Why Measles Cases Are Rising

After years of progress, learn why measles is making a comeback and how to protect yourself.

toddler infected with measles

Updated on March 15, 2024.

For parents who are unsure or hesitant to vaccinate their children, here’s a wakeup call: Measles outbreaks are on the rise again.

As of March 7, 2024, a total of 45 measles cases were reported in 17 states: Arizona, California, Florida, Georgia, Illinois, Indiana, Louisiana, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York City, Ohio, Pennsylvania, Virginia, and Washington, the U.S. Centers for Disease Control and Prevention (CDC) reports.

Only a few months into the year, there are roughly as many new cases or more as there have been for the entire year in 2023 (58 cases), 2021 (49 cases), and 2020 (13 cases). If cases continue to rise, experts caution the outbreak could threaten the United States’ measles elimination status.

In the U.S., thanks to widespread, routine childhood vaccination with the MMR (measles, mumps, rubella) vaccine since 1971, measles was declared eliminated in 2000, according to the Centers for Disease Control and Prevention (CDC).  

But for many reasons, including lingering misconceptions about vaccines, fears about a link between the MMR shot and autism (which stem from a false report that was retracted and discredited decades ago), and delayed or missed vaccines during the pandemic, an increasing number of parents have not vaccinated their children. As a result, measles outbreaks are occurring in areas where there are larger groups of unvaccinated people.

Some parents don’t immunize their children because they think the diseases being prevented are not common enough to worry about—or they’re concerned about vaccine safety, says Anthony Komaroff, MD, Distinguished Simcox-Clifford-Higby Professor of Medicine at Harvard Medical School and Senior Physician at Brigham and Women's Hospital in Boston.  

But the benefits of vaccination outweigh the risks. “Infectious diseases are still widespread around the world,” he says, noting that “all vaccines are carefully studied before they are licensed for routine use.”

The last major outbreak since 1992

In 2019, confirmed cases in the United States reached the highest level in 28 years. Overall, in the U.S. that year there were 1,282 confirmed cases of measles in 31 states. It is the greatest number of cases reported in the U.S. since 1992 when 963 cases were reported for the entire year. It's also the highest number of cases since measles was declared eliminated.

By 2019, measles cases had already been trending upward. Between 2015 and 2017, there were between 86 and 188 confirmed cases each year. But in 2018, there were a total of 372 confirmed cases of measles across the United States.

When enough people in a population are vaccinated against a disease to prevent it from spreading, it is called herd immunity. But herd immunity also depends on how contagious a disease is, or how easily it spreads.  Since measles spreads from person to person very easily, it’s estimated that 95 percent of a population needs to be vaccinated to stop it from spreading.

The latest CDC statistics show that about 91 percent of children are vaccinated against measles by the age of 2. But research conducted during the COVID pandemic suggest the public health emergency disrupted routine childhood vaccination. In 2020, the percentage of children around the world who were vaccinated against measles dropped to 84 percent. Another 2020 model-based study found that a continuing reduction of measles vaccinations among 1-year old children in the United States could push vaccination rates below 80 percent.

There is evidence that routine childhood vaccination coverage is rebounding, but unevenly, according to the CDC. Some parts of the country and certain groups of people have less protection than others. The rebound may also not be enough to achieve “catch up” coverage—or making sure all those who have missed vaccine doses become immunized.

Kids who miss out on routine immunization may also be at risk other vaccine-preventable diseases, including diphtheria, tetanus, pertussis, and varicella (chicken pox).

“This means every year children get severe illnesses and possibly even die from diseases that could have been prevented by a vaccine,” Dr. Komaroff cautions.

The MMR vaccine is safe

The MMR vaccine is given in two shots, the first at age 12 to 15 months, the second between the ages of 4 and 6 -years old. Study after study, including a 2014 analysis published in Pediatrics and a 2020 review publish in Frontiers in Microbiology, has shown that this vaccine is safe and does not cause autism in children who receive it.

In 2011, an Institute of Medicine (IOM) report, which examined eight vaccines given to both kids and adults, found that they are very safe. Then, in 2013, a CDC study examined the immune response to the vaccine in children during the first two years of life. They found no differences between kids with autism and those who did not have this condition.

More recently, a March 2019 study published in the Annals of Internal Medicine, analyzed the safety of the MMR vaccine even more rigorously. Researchers in Denmark used larger populations of children (hence more statistical power) to investigate concerns about a link between the vaccine and autism. They also included a larger number of children considered at high-risk for autism to address the specific claim that the MMR vaccines may be more dangerous for these kids, in particular.

The scientists evaluated whether the MMR vaccine increased the risk of autism in 657,461 children born in Denmark between 1999 and 2010. They tracked the kids until August 2013, documenting diagnoses of autism spectrum disorders and risk factors for these conditions, including parents’ ages, siblings with autism, method of delivery, smoking during pregnancy, preterm birth, and low birth weight.

The study found no evidence of a link between the MMR vaccine and autism or an increased risk for these disorders—even among high-risk kids.

Measles can be dangerous—even deadly

The most common side effects of the MMR include mild rash, fever, or temporary discomfort in the arm where the shot was given. By comparison, getting measles is far worse and more serious.

Measles symptoms usually appear seven to 14 days after exposure. But they are considered contagious four days before they show signs of infection.

An infected person will develop a fever and fatigue. Before long, they will start to cough and get a runny nose. They may also have conjunctivitis, also known as pinkeye.

About two days after these symptoms appear, tiny white spots, called Koplik spots, may form inside their mouth. Three to five days after symptoms begin, patients will break out in the characteristic red measles rash. First, it will appear on their face before spreading to their chest, arms, legs, and feet. At this point, their fever may spike to more than 104 degrees Fahrenheit.

Those infected may continue to be contagious or spread the virus to others for four days after the rash appears.

Measles can also cause ear infections, diarrhea, and pneumonia. More rarely, it can lead to encephalitis (inflammation of the brain), which may be fatal. This risk for serious complications or death resulting from a measles infection is greater for infants than young children or adults.

There is no way to cure measles once someone is infected. “The only treatment centers around trying to lessen the severity of the disease and making your child as comfortable as possible,” says the Honor Society of Nursing (STTI). STTI recommends using a humidifier to ease sore throat and coughing and giving acetaminophen or ibuprofen for fever.

Article sources open article sources

Centers for Disease Control and Prevention. Measles Cases and Outbreaks. Mar 2024.
PAMELA G. ROCKWELL, DO, The Family Physician's Role in the Prevention of Measles Am Fam Physician. 2019;100(6):329-330
Centers for Disease Control and Prevention. Measles, Mumps, and Rubella. Sept 2023.
Maltezou HC, Medic S, Cassimos DC, Effraimidou E, Poland GA. Decreasing routine vaccination rates in children in the COVID-19 era. Vaccine. 2022 Apr 20;40(18):2525-2527. doi: 10.1016/j.vaccine.2022.03.033. Epub 2022 Mar 22. PMID: 35341648.
Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Report (MMWR). Impact of the COVID-19 Pandemic on Administration of Selected Routine Childhood and Adolescent Vaccinations — 10 U.S. Jurisdictions, March–September 2020 Weekly / June 11, 2021 / 70(23);840–845.
World Health Organization. Catch-up vaccination. Accessed Mar 2023.
Immunize.org. Ask the Experts: MMR (Measles, Mumps, and Rubella). Jun 2023.
Sarah Geoghegan; Kevin P. O’Callaghan; Paul A. Offit, Vaccine Safety: Myths and Misinformation. Front. Microbiol., 1Vol 11, 6 March 2020.
Lidia V. Gabis,Odelia Leon Attia,Mia Goldman, et al. The myth of vaccination and autism spectrum. European Journal of Paediatric Neurology Jan 2022.
Anders Hviid, Jørgen Vinsløv Hansen, Morten Frisch, et al. Measles, Mumps, Rubella Vaccination and Autism: A Nationwide Cohort Study. Ann Intern Med.2019;170:513-520. [Epub 5 March 2019].
Maglione MA, Das L, Raaen L, Smith A, Chari R, Newberry S, Shanman R, Perry T, Goetz MB, Gidengil C. Safety of vaccines used for routine immunization of U.S. children: a systematic review. Pediatrics. 2014 Aug;134(2):325-37. doi: 10.1542/peds.2014-1079. Epub 2014 Jul 1.

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