British researchers have confirmed that the measles-mumps-rubella (MMR) vaccine can cause a rare bleeding disorder in children.

But they stress that children remain at much higher disease risk from measles, mumps or rubella if they forego vaccination, than they are from the vaccine-linked bleeding condition, called idiopathic thrombocytopenic purpura (ITP).

People with ITP bleed under the skin, causing a kind of purple bruise to spread across the body. Other symptoms can include tiny red spots on the skin and nosebleeds. The condition is mild in the majority of cases.

The reaction, caused by the destruction of the platelets that help blood clot, seems to occur most often within the first 2 or 3 weeks of receipt of the vaccine according to the American Academy of Pediatrics.

The vaccine has been linked to the disease for years, although evidence supporting the association has been limited.

The absolute risk of hospitalization for ITP within six weeks of immunization was 1 in 22,300 doses.

ITP can occur in children following a viral infection. Miller and colleagues note that the vaccine-related risk is quite low when compared to ITP that occurs after catching measles, rubella or mumps. For instance, one case of ITP occurs for about every 3000 rubella infections.

Archives of Disease in Childhood March 2001; 84: 227-229