The MMR vaccine is a combination vaccine made up of three live, attenuated viruses -- measles, umps, and rubella. Each individual vaccine was introduced in the 1960s, and the combination has been licensed since 1971.
The vaccine is given as a subcutaneous injection. This means that the needle, which is attached to a syringe filled with the vaccine mixture, is placed under ('sub') the skin ('cutaneous'), rather than in the muscle, as some other vaccines may be given.
What Are the Diseases That MMR Vaccines Protect Against?
The MMR vaccine protects against measles, mumps, and rubella. Each of these three viral diseases are associated with severe and devastating complications, and no treatments are available for these diseases. MMR vaccines are very effective and very safe, providing lifelong immunity in most people who get vaccinated.
These diseases are:
Measles, or rubeola, is a leading cause of death of young children worldwide. It has been called “the most infectious of microbial agents,” since prior to 1963, when the vaccine was introduced, nearly all children got the disease. People who get measles are at relatively high risk for complications, including brain infections and blindness.
Mumps is a common childhood infection with several potential complications, including inflammation or swelling of the brain, testis, heart, and joints. Its most characteristic symptom is swelling of the salivary glands, making patients appear to have 'chipmunk cheeks.'
Rubella, also called German measles, is a viral disease that is characterized by a red rash. It is known to cause severe and devastating defects in unborn babies, including heart defects, mental retardation, bone alterations, vision abnormalities, and hearing loss.
Who Should Get Vaccinated?
The MMR vaccine is recommended for all children. The first vaccine should be give around 12 to 15 months, and the second one at ages 4 to 6 years, just prior to entry into kindergarten.
Adults who have not been vaccinated should receive at least one dose. Those who work in health care or in a school or university setting are at higher risk for exposure and should get two doses.
Who Should Not Get Vaccinated?
Pregnant women and people with weakened immune systems should not get the vaccine. Why? The vaccine is made with live, attenuated viruses, meaning the viruses are in a weakened form and cannot survive in people with healthy immune systems. In people whose immune systems are weakened, the attenuated virus may be strong enough to survive and establish an infection.
In addition, because of additional ingredients of the MMR vaccine, people with severe allergies to gelatin or neomycin (an antibiotic) should not get the vaccine.
How Effective Is It? Why Are Two Shots Needed?
A single vaccination with MMR is effective in 80% of people, and two doses will protect against disease in 90% of people.
The second dose is not considered a “booster” shot, as it does not increase immunity in a person who has already been vaccinated. Rather, the second dose is intended to produce immunity in the small percentage of individuals who did not respond to the first dose.
How Safe Is It? Are There Any Side Effects?
MMR vaccine is very safe. A small percentage of children (1 in 5) will get a mild rash or fever about 1 to 2 weeks after the vaccine. These side effects will last up to 3 days. Febrile seizures (seizures caused by fevers) have occasionally been reported, but have not been associated with long-term problems. Swollen lymph glands and joint swelling may occur in a very small percentage of patients. Less than one in a million patients receiving the vaccine have developed encephalitis (brain inflammation), but health experts have not conclusively determined whether or not a link exists.
Does It Cause Autism?
The MMR vaccine does not cause autism. A study published in The Lancet medical journal in 1998, authored by Dr. Andrew Wakefield, implicated the MMR vaccine as a cause of autism. Ensuing widespread panic lead to a significant decrease in the number of children receiving the MMR vaccine and a subsequent increase in the number of cases of measles, mumps, and rubella.
In a 2009, in a disciplinary hearing by the General Medical Council, it was determined that Dr. Wakefield manipulated patients’ data and the study has been discredited. Numerous well-designed and very large studies have repeatedly demonstrated no association between MMR and autism. On February 12, 2009, a U.S. federal court ruled that vaccines do not cause autism.
Centers for Disease Control and Prevention. Vaccine Safety. Measles, Mumps, and Rubella Vaccine. Accessed February 26, 2009. http://www.cdc.gov/vaccinesafety/concerns/mmr_vaccine.htm
Centers for Disease Control and Prevention. Vaccines & Preventable Diseases. Accessed February 26, 2009. http://www.cdc.gov/vaccines/vpd-vac/