How falling vaccination rates are fueling measles outbreaks

Published on Saturday, March 1, 2025

By: Rachel Vanderford, rvanderford@umc.edu

Measles, once considered eradicated in the United States, has resurfaced at an unsettling rate in 2025, reflecting the importance of vaccination.  

As of March 13, the Centers for Disease Control and Prevention reported 301 confirmed cases across 15 jurisdictions: Alaska, California, Florida, Georgia, Kentucky, Maryland, New Jersey, New Mexico, New York City, New York State, Pennsylvania, Rhode Island, Texas, Vermont and Washington. This resurgence includes the first measles-related death in the US in a decade—a school-aged child in Texas who had not been vaccinated.

Measles is an exceptionally contagious viral disease that spreads through respiratory droplets when an infected person breathes, coughs or sneezes.  

“Measles spreads incredibly fast and easily. A single case can quickly expose large groups of people, especially in communities with lower vaccination rates,” said Dr. Roberto Santos, professor in the Division of Infectious Diseases. “Unvaccinated individuals are at a high risk of severe complications, and outbreaks can escalate rapidly.” 

Before the introduction of the measles vaccine in 1963, the virus caused widespread epidemics every two to three years, leading to approximately 2.6 million deaths globally each year. The development of the measles vaccine marked a turning point, drastically reducing the incidence of the disease. By the year 2000, measles was considered eradicated in the United States. 

Early symptoms of measles typically appear 10 to 14 days after exposure to the virus. Early symptoms include a high fever, cough, runny nose and red, watery eyes. Small white spots, known as Koplik spots, may also appear inside the mouth. Seven to eighteen days after exposure, a characteristic red rash usually begins on the face and upper neck, then spreads to the hands and feet over the course of about three days. 

While most individuals recover within a few weeks, measles can lead to severe complications, especially in children under five and adults over 30.  

“Severe complications of measles may include brain inflammation (encephalitis) or severe pneumonia to name a few,” said Santos. “It is important to remember that we don't have a specific antiviral agent to treat measles that is why it is better to be vaccinated against this preventable disease.” 

The Measles, Mumps and Rubella (MMR) vaccine is a safe and effective tool in preventing measles infections. The vaccine contains weakened forms of the viruses, which must multiply to create an immune response. 

Because newborns’ natural protections against illness wear off as they grow older, the CDC recommends that children receive two doses: the first at 12 to 15 months of age and the second at 4 to 6 years. Two doses of the MMR vaccine are approximately 97% effective at preventing measles.  

For herd immunity to be effective against measles, a high level of population immunity is required due to the virus’ high transmissibility.  

Nationally, vaccination rates have declined in recent years, partly due to increased vaccine hesitancy. During the 2023-24 school year, vaccination coverage among kindergarteners in the U.S. decreased for all reported vaccines from the year before, including MMR at 92.7%. 

In 2024, 97.5% of Mississippi school children received the MMR vaccine, still above the national average but a decrease from 2019, when the state had the highest vaccination rate in the nation at 99.1%. 

“We remain respectful to the family’s decision to vaccinate or not vaccinate their family; however, a thorough discussion with your medical provider should take place regarding the pros and cons of your medical decision,” Santos said.  

“Measles remains a vaccine preventable disease and, in some cases, may progress to severe disease particularly those with immunocompromising conditions, including but not limited to those with severe primary immunodeficiency, patients who have received a hematopoietic cell transplant or patients on treatment for leukemia, and patients with HIV with severe immunosuppression.” 

This has resulted in pockets of unvaccinated individuals, making communities more susceptible to outbreaks. During a measles outbreak, about one in five people who get sick will need hospital care and one in twenty will develop pneumonia. 

There have been 3 outbreaks, defined as three or more related cases reported so far in 2025, and 93%(280 of 301) of total cases are outbreak-associated. For comparison, 16 outbreaks were reported in 2024 and 69% of cases (198 of 285) were outbreak-associated. 17% of cases have been hospitalized this year.

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