There’s more bad news for advocates of the MMR (measles-mumps-rubella) vaccine with the discovery this week that it can cause a blood disorder.  Researchers have found that it may trigger immune thrombocytopenic purpura (ITP), an immune system malfunction that destroys the body’s own blood platelets.

The effect seems to last for an average of seven days, during which time the child’s platelet count could fall.

The risk is relatively low, say researchers, and one case of ITP will be caused per 40,000 vaccinations.  The risk appears to last for up to 42 days after vaccination.

Researchers from Kaiser Permanente Colorado, Denver analysed the health profiles of more than 1 million children who had been vaccinated.  Of these, 259 developed ITP, and they reckon the vaccine was responsible for 76 per cent of these cases.

(Source: Pediatrics, 2008; 121: e687-e692).

* CLARIFICATION:  Several readers responded to last week’s news story about the child who developed autism after receiving the MMR and other vaccinations.  They were concerned by the suggestion that the MMR vaccine contains the preservative thimerosal, and, of course, the live vaccine doesn’t.  However, the article didn’t say it did either.  The story stated that the child received nine vaccines, including the MMR, and two of them contained thimerosal.