Having the MMR vaccine does not overload a child's immune system, preventing it from fighting other infections, researchers say.
The MMR vaccine is given in one jab
It had been feared that being given the combined measles, mumps and rubella jab would be too much for a child.
To test the theory, researchers looked at serious bacterial infections such as septicaemia, pneumonia and meningitis amongst one to two-year-olds.
MMR is the only vaccination given to children of that age.
If it did affect the immune system, the researchers said, they would have expected to see an increase in infections just after children had been given the jab.
We want the vaccine policy makers to do is do a study on the children believed to have been damaged by MMR
But the researchers, from the Public Health Laboratory Service (PHLS), said there was no evidence that having the MMR vaccination increased the risk of developing an infection then, compared to before having the jab or a long time after.
The said there could even be a protective effect from the jab.
There have been concerns that MMR vaccination is linked to increased rates of autism and bowel disease, but experts say there is no evidence that this is the case.
Fears over the potential link have led some parents to decide to give their children the immunisations separately.
Parents' concerned that having three vaccinations at the same time is too much for their child's immune system should be very reassured that this is not the case
Dr Elizabeth Miller, Public Health Laboratory Service
The researchers looked at data from hospitals in the Thames region of south east England relating to 436 children admitted with serious bacterial infections between April 1991 and March 1995.
Forty one cases were excluded because they had an
underlying condition or were being readmitted.
Of the remaining children, 116 had an invasive bacterial infection and 279 had
They looked to see if children were more likely to develop an infection in the three months immediately after being given the MMR jab, but found there was no increased risk.
Dr Elizabeth Miller, who led the research, told BBC News Online: "Parents' concerned that having three vaccinations at the same time is too much for their child's immune system should be very reassured that this is not the case.
"And it's certainly no reason at all to consider having separate vaccines."
'Children - not data'
But Jackie Fletcher, founder of the campaign group Jabs, said: "We don't think this report is looking at the right group of children.
"And they weren't looking at children themselves, they were looking at hospital admission data.
"What we want the vaccine policy makers to do is do a study on the children believed to have been damaged by MMR."
The study is published in the journal Archives of Disease in