Measles cases are increasing in nine states across the US: Alaska, California, Georgia, Kentucky, New Jersey, New Mexico, New York, Rhode Island, and Texas. The biggest outbreak has been in Texas, which as of February 24, 2025, reported 124 measles cases and is expected to continue to grow. On February 26, 2025, Texas reported the first death from this outbreak in a school-aged child who was unvaccinated.
What is Measles?
Measles is a disease caused by the highly contagious measles virus. This virus easily spreads person to person through the air when an infected person breathes, coughs, or sneezes. Common symptoms of measles include a high fever, cough, runny nose, and a specific rash all over the body. However, 3 in 10 people who get measles experience complications.
Minor complications of measles include ear infection or diarrhea, which affect 1 in 10 children with measles. Severe complications of measles include hospitalization affecting 1 in 5 people, pneumonia affecting 1 in 20 people, and brain swelling (encephalitis) which affects 1 in 1000 children who get measles. A rare, but long-term complication of measles is subacute sclerosing panencephalitis (SSPE), which is a fatal disease impacting the nervous system. SSPE is caused by prior measles infection and can develop seven to ten years after a person had measles. Since 2000, SSPE has rarely been seen in the US however, as outbreaks continue, the possibility of seeing SSPE increases.
Unfortunately, 1 to 3 of every 1000 children who get measles will die from respiratory or neurologic complications. Before a vaccine was available, nearly every child had measles before they turned fifteen, making the risk of severe complications very dangerous.
MMR Vaccine is Safe and Saves Lives
Between 2000 and 2023, measles vaccination averted more than 60 million deaths worldwide. In the US, children are vaccinated against measles with the MMR (measles, mumps, and rubella) vaccine first at 12-15 months and then with a booster dose at four years old. Two doses of the MMR vaccine are 97% effective at preventing disease and provide long-term immunity, making vaccination against measles highly effective. The measles vaccine has been studied extensively and has been found to be very safe, with no link to autism. Being vaccinated is the best way to prevent disease or spreading measles virus to other people.
Since vaccination with two doses of the MMR vaccine is highly effective and immunity is long-term, vaccination rates above 95% decrease the likelihood that measles is spread to people who are not vaccinated. This protection is referred to as herd immunity. Herd immunity provides protection for people who can’t receive the vaccine, such as infants who aren’t old enough to receive the vaccine and people with a weakened immune system.
Unfortunately, if vaccination coverage declines, the chance of a measles outbreak increases. Since 2008, outbreaks in the US have largely been in unvaccinated individuals. The is the pattern seen in Texas, where 119 of the 124 cases are in unvaccinated individuals.
Measles and the Immune System
A unique and dangerous aspect of measles is the impact the virus has on the immune system. Measles virus can reset the immune system of an infected person causing the immune system to lose its memory on how to eliminate previously encountered pathogens in what is called ‘immune amnesia.’
This happens because the virus attaches to special immune cells, called memory T-cells and memory B-cells. These cells remember a pathogen (such as a virus) that your body has encountered before and produce antibodies needed to eliminate it. To clear an infection, the body must destroy infected cells, which in this case includes the memory T and B cells with the measles virus attached to them. Unfortunately, this destroys the immunological memory along with the cells and the virus. At the same time, your immune system generates new memory T and B cells specifically to fight the measles virus. This leaves you with immunity to measles but can leave you vulnerable to other previously encountered pathogens for which the memory cells have been eliminated.
Studies comparing infectious diseases in children before and after measles vaccination have found that nearly 50% of childhood deaths from infectious disease were due to the impact of immune amnesia. It is estimated that it takes two-three years to restore immune memory in children affected by immune amnesia.
This is just one of the many reasons it is important to get the MMR vaccine and protect your child from measles. The best way to prevent measles is to receive two doses of the measles vaccine. If you think you were exposed to someone with measles, are experiencing symptoms, or would like to get a vaccine, contact your doctor or local health department.