Slight Risk of Bleeding Disorder No Reason to Avoid MMR Vaccine

Feb. 22, 2001 -- A recent episode of the television show ER dealt with the case of a 4-year-old child who died from complications of measles. He contracted the disease because his mother worried about possible (but unproven) side effects from the measles-mumps-rubella (MMR) vaccine and failed to immunize him.

As physicians have long suspected and British researchers now confirm in a study published in the journal Archives of Disease in Childhood, there is a very slight risk that children who receive the MMR vaccine will develop a treatable rash-like condition called idiopathic thrombocytopenic purpura, or ITP. But children who don't get the vaccine are much more likely to get ITP and are at grave risk for serious complications such as pneumonia, diarrhea, seizures, brain damage, hearing loss, and death from measles.

"Although our study shows that some children are admitted to hospital for ITP, even in these cases the disease is rarely dangerous and can be easily treated. This is in stark contrast to measles, mumps, and rubella, which can have very serious consequences and be difficult to treat. The risks associated with ITP are small when compared to those of the diseases which this vaccine is designed to prevent," says lead author Elizabeth Miller, MD, head of the immunization division at the Public Health Laboratory Service communicable disease surveillance center in London, in a written statement.

ITP is a bleeding disorder resulting from a shortage of blood cells that help the blood to clot. People with ITP bruise easily and have characteristic purple patches caused by bleeding under the skin. In children, it may occur following a viral infection and usually resolves itself without treatment, although some patients may require hospitalization in order to control the bleeding.

In their study, Miller and colleagues looked at hospital admissions for ITP in children in two regions of England and calculated that 1 in every 22,300 MMR vaccinations would result in hospital admission for ITP. They also estimate that for cases of ITP occurring within six weeks of MMR vaccine, two out of three are probably linked to the vaccine. But they also found that the risk of ITP is high after natural measles infections and follows about 1 in 3,000 rubella cases, and that more than 70% of ITP cases occur following a viral infection.

The researchers also offer reassuring evidence that the vaccine does not appear to cause new ITP cases or reactivate ITP in children who have had the bleeding disorder before. In addition, the few cases of ITP that could be linked to the MMR vaccine appeared to be milder than others, they report.

"It confirms what was previously thought to be the case, which is that if you get the MMR [shot] you are at a low but real risk of developing idiopathic thrombocytopenic purpura within 6 weeks after the immunization," says Richard Malley, MD, assistant professor of pediatrics at Harvard Medical School and a staff physician in the division of infectious diseases at Children's Hospital, Boston.

Malley, who reviewed the study for WebMD, says that it confirms the benefits of immunization with MMR.

"If a parent thought, 'Well, I want to interpret these results as suggesting to me that I should not immunize my child because I don't want him to get ITP,' I would answer that, first of all, if you don't immunize the child, the risk is greater that he'll get a serious illness -- mostly measles, which is still around and has a lot more complications than just ITP," he explains. "But in addition, if the concern is mostly ITP, the risk ... for getting ITP should they get measles is significantly greater than [the risk of] getting ITP from MMR [vaccine]."

Despite persistent rumors to the contrary about vaccine safety, there is no credible scientific evidence to suggest that the MMR vaccine -- or any other vaccine, for that matter -- can cause autism, and although some people may object to immunization for religious or personal reasons, there is no solid medical ground under the feet of those who claim that childhood vaccines are unduly risky.

Miller says some rumors suggest that researchers are reluctant to reveal information on the adverse side effects of vaccines. "This paper shows that this is simply not the case -- we do extensive work on adverse reactions, and where we suspect that an adverse reaction occurs, we are committed to researching it, providing evidence about it, and making that evidence publicly available," she says in the written statement. "Equally, however, where the doubts are unfounded, as with the MMR and autism issue, we are committed to refuting those claims. We urge parents to protect their children against measles, mumps, and rubella with the MMR vaccine."