The MMR vaccine protects your child against three viral diseases -- measles, mumps, and rubella -- all of which are spread from person to person through the air.
Measles is a highly contagious infection that causes a rash all over the body, cough, runny nose, eye irritation, and fever. If left untreated, the infection can lead to ear infections, pneumonia, seizures, brain damage, and even death. Until the MMR vaccine became available in the 1970s, nearly all children in the U.S. had measles by the time they were 15 and nearly 50,000 people were hospitalized each year.
The mumps virus is most known for its telltale chipmunk cheeks, caused by swollen glands in the jaw. Serious infections can lead to permanent hearing loss, meningitis (an infection of the lining of the brain and spinal cord), painful swelling of the testicles or ovaries and, rarely, even death. Like measles, mumps used to be a common illness in infants, children and young adults.
Rubella, also known as German Measles, is an infection that causes rash, mild fever, and arthritis. Women who get the disease while pregnant are at risk for miscarriage or having a baby with serious birth defects. Before the MMR vaccine was available, a rubella outbreak in the U.S. caused 12.5 million people to get the disease in one year -- and 20,000 babies were born with birth defects as a result.
After decades of vaccination in the U.S., all three of these diseases were all but eliminated here. But when unvaccinated people contract one of the diseases and spread it to others who haven't been vaccinated, outbreaks can occur. In December 2014, a measles outbreak started in Disneyland and has spread to at least 17 states on the west coast. Over 150 cases of measles have been confirmed as of this writing.
The usual MMR vaccine schedule includes two doses for kids: one between 12 and 15 months and the second between ages 4 and 6.
But the American Academy of Pediatrics (AAP) updated their vaccine schedules in January 2015 to include guidelines for babies under 12 months who are traveling outside the country. These babies should receive three doses (the first between 6 and 11 months, the second between 12 and 15 months, and the third about four weeks after the second dose).
For kids older than 12 months who are traveling outside the country, they should receive two doses of the MMR vaccine, the first one between 12 and 15 months and the second one about four weeks later.
The MMR vaccine is safe to be given along with other vaccines. It is also available as a combination shot with the chickenpox vaccine (called MMRV). This version of the shot isn't as readily available as the stand alone MMR and chickenpox vaccines, so it's not yet widely used. Children who receive MMRV may be more likely to experience side effects like rash, fever, and febrile seizures than those who get the MMR and chickenpox vaccines separately.
Despite persistent rumors, there is no scientific evidence that the MMR vaccine causes autism.
In 1998, a British doctor named Andrew Wakefield published a very small study (it only included 12 kids) in a British medical journal, The Lancet. The study claimed that children developed autism soon after they received the MMR vaccine. The theory: The measles portion of the shot causes inflammation that may lead to brain damage and trigger the onset of autism.
In early 2010, The Lancet retracted the research and in January 2011, an editorial in the British Medical Journal publicly denounced Dr. Wakefield's research as "fraudulent" and revealed that he "falsified data" by tampering with the research results to give the vaccine bad publicity. At the time of his study, Dr. Wakefield had been involved in a lawsuit against the manufacturers of the MMR vaccine and would have gained money if he'd won, making his research an obvious conflict of interest.
Today, most scientists believe that parents may mistakenly blame the MMR vaccine for causing autism because early autism symptoms tend to first show up between 12 and 15 months, which is around the same time the vaccine is administered. But major groups of experts -- including the American Academy of Pediatrics and the Institute of Medicine -- agree that the MMR vaccine has not had any effect on autism rates.
While the MMR vaccine is one of the Centers for Disease Control and Prevention's (CDC's) recommended childhood vaccinations, children who fall into the following categories should not receive it:
Talk to your doctor if you're concerned about whether or not the MMR vaccine is safe for you or your child.
Contracting measles, mumps, or rubella is more dangerous than any side effects from the vaccine. Though allergic reactions are possible, the MMR vaccine generally only causes mild side effects.
As with any vaccine, severe allergic reactions are rare, but possible. If you notice your child having difficulty breathing, hoarseness or wheezing, hives, paleness, weakness, dizziness, or a rapid heartbeat shortly after he receives a shot, call your doctor right away.
Because measles, mumps, and rubella nearly disappeared from the United States, some people may think that getting vaccinated is no longer necessary. But the recent and sudden measles outbreak shows this is not so.
Just because these diseases are no longer as widespread doesn't mean we're completely immune -- outbreaks can and still do happen, usually because of some children skipping immunizations, says Neal Halsey, MD, director of the Institute for Vaccine Safety at the Johns Hopkins University Bloomberg School of Public Health in Maryland. "In order to prevent other future outbreaks -- and keep our children healthy -- it's crucial that we continue to get our kids vaccinated against these diseases completely and on time."
Reviewed and updated in 2015.
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