A mother is challenging a High Court order which would force her to send her daughter for the controversial MMR jab.
The court ruled the children should be given the MMR jab
A judge ruled on Friday that the child and another girl should be given the vaccination, as their fathers wanted.
It is understood both mothers had expressed concerns over the jab's safety, although the vast majority of experts say there is no risk to health.
Now the mother of one of the girls says she will appeal against the High Court decision.
Nick Skeens, a family friend helping the mother, said: "The judgment came through without us being informed. It took us all a bit by surprise."
The girl's mother said another freedom had been "eroded" by the court's decision.
She said in a statement: "It's outrageous that, in a free society, a judge could make such a decision.
The High Court ruling means her daughter and another girl, who is 10, must now be given the jab.
Mr Justice Sumner also ruled that the girls should be immunised against other diseases, including diphtheria, tetanus, whooping cough, polio, and meningitis.
His decision could have implications for other parents across the UK, who disagree over whether their children should receive the MMR vaccine.
Some campaigners have suggested the jab may be linked to autism and bowel disease. However, these claims have been dismissed by doctors and the government, who all insist it is safe.
Experts have also warned that a drop in vaccine rates could lead to a resurgence
in measles, a highly contagious illness that can cause
pneumonia, brain damage, dementia and death.
Mr Justice Sumner ruled that it was in the girls' best interests to be given the three-in-one jab.
He rejected the idea of giving the girls separate vaccinations against mumps, measles or rubella, saying that the gap between jabs could put them at risk of getting these diseases.
Both girls in this case live alone with their mothers. Their parents are either divorced or separated.
None of those involved in the case can be identified for legal reasons.
Mr Justice Sumner said his decision was influenced by evidence given by medical experts.
He indicated that he had considered the ruling carefully.
"There are considerations which have weighed heavily with me," he said.
"I accept a parent's right to choose whether they accept medical advice to
have immunisation for their children or not."
But he added: "Recognising the anxieties of the mothers and that an adverse decision will be upsetting, the children's best interests are served by receiving a programme of immunisations and an order should be made."