Measles
Learn about measles virus and the vaccine that prevents it.
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Overview
Measles is a disease caused by the measles virus. The virus is highly contagious, and infection can cause serious complications. Measles used to be a common childhood illness, but the measles vaccine has caused cases in the United States to dramatically decrease. However, vaccination rates need to remain high to prevent cases of measles.
Key Points
- Measles virus is highly contagious and can cause serious complications for those who get infected.
- There is a safe and highly effective measles vaccine available. However, vaccination rates need to remain high to prevent the spread of measles.
- Measles infection can cause the immune system to lose its memory and forget how to fight previously encountered pathogens.
What is Measles?
Measles is a disease caused by the highly contagious measles virus. This virus easily spreads from 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, pneumonia, and brain swelling (encephalitis). 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 increase, 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.
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.
The Measles Vaccine
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 community immunity. Community immunity provides protection for people who can’t receive the vaccine, such as infants who aren’t old enough or 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 MMR vaccine in the US is covered by insurance and the Vaccines for Children program, which provides free vaccines to children without insurance. If you would like to learn more, talk to a doctor or visit a local health clinic.
Sources
Measles Vaccination: Know the Facts, Infectious Disease Society of America
- Measles, World Health Organization
- Long-Term Measles-Induced Immunomodulation Increases Overall Childhood Infectious Disease Mortality, Science
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