In fact, the vaccine seems to protect children from such infection, says the study by researchers at the Public Health Laboratory Service. The report appears in the current issue of Archives of Disease in Childhood.

They monitored all cases of serious bacterial infection, such as septicemia, meningitis and pneumonia, among 436 1- to 2-year-old children admitted to a number of southern England hospitals within three months of receiving an MMR vaccine.

The monitoring was done from April 1991 to March 1995.

The researchers excluded 41 cases because the children had underlying health conditions or were hospital readmissions. Of the remaining children, 116 had invasive bacterial infection and 279 had pneumonia.

However, after the researchers factored in the background prevalence of a given infection, they concluded there was no evidence the MMR shot increased the risk of serious infection. Instead, the shot seemed to provide protection against pneumonia.

The study results contradict the popular notion that the MMR shot impairs the immune system and increases infection susceptibility.

More information

Here's where you can learn more about children's immunizations.