A 15-year-old girl and her 11-year-old sister should receive the MMR vaccination, against the wishes of the youngsters and their mother, a High Court judge has ruled.
Vaccination is in the best interests of the girls, Mrs Justice Theis concluded after a hearing in the Family Division of the High Court in London.
The judge said the children cannot be identified.
She made the ruling on September 5, after a private hearing on July 31, and it was published today on a legal website after the BBC learned of the case and reported the result.
An MP who campaigns for improvements in the family justice system criticised Mrs Justice Theis for failing to publish the ruling earlier.
Mrs Justice Theis said the girls' father - who is separated from their mother - asked the court to order the vaccination.
The couple were married in 1996 but this had broken down in 2009 and they separated in 2011, the judge said.
Both girls live with their mother but have contact with their father.
The older girl was inoculated, by agreement between her parents, soon after her birth. Later the couple decided that the older girl should not receive a booster and decided that the younger girl should have no vaccinations, the judge said.
The father told the court that he was a "reluctant participant in the joint decision not to inoculate", said the judge.
"In 1998 there was great public debate about the MMR vaccine. Much of the controversy surrounded the research paper, published in The Lancet, by Dr Andrew Wakefield which cast doubt on the vaccine's safety and the risks said to be attached to administering it, particularly in relation to the possibility of autism," she said.
"As a consequence of this, the parties decided, in consultation with their GP, that (the older girl) should not receive her booster, and (the younger girl) has had no vaccinations at all.
"The father now states he was a reluctant participant in the joint decision not to inoculate. He says he has become increasingly concerned that the girls have not been immunised and were not protected.
"Dr Wakefield's research paper was later discredited. The Lancet subsequently retracted Dr Wakefield's paper and his research was not approved by the General Medical Council.
"The NHS, General Medical Council, Chief Medical Officer and the World Health Organisation all recommend that children should have this vaccine.
Mrs Justice Theis added: "He is concerned that the consequences of contracting measles, mumps and rubella are serious. He states the need for the children to have protection has been brought into sharper focus following (a) recent outbreak of measles in Wales."
Mrs Justice Theis said the girls' mother questioned the benefits of the vaccine, worried about possible side effects and was concerned about the impact of the vaccination being undertaken against the girls' wishes - in particular the older girl who had "psychological problems" and was a vegan and worried about the vaccine containing animal-based ingredients.
"I have reached the conclusion it is in the best interests of (both girls) that they receive the MMR vaccination," said the judge.
"Whilst I am acutely aware of both (girls') wishes and feelings ... I consider their views have inevitably been influenced by a number of factors which affects the weight that should be attached to those wishes and feelings.
"First, from their perspective the parents were initially united in their decision for them not to be vaccinated and they can't understand why their father has changed his mind."
She added: "Second, they have become focussed (sic) on the issue of the ingredients of the vaccine without being able to consider and balance the wider picture, and the consequences or actions of them not having it, including medication (and its contents) that would be required in the event of them becoming ill from one of the vaccine-preventing diseases.
"Third, it is not surprising that they are likely to have become influenced by their mother's views. Those views are clearly strongly held and will inevitably have influenced both children."
The judge said she had carefully considered the emotional needs of both girls.
"They are inevitably caught in the middle of this dispute between their parents. The consequence for them emotionally of the court reaching a decision that does not accord with their wishes is a factor to bear in mind," said the judge.
"However, as with most issues concerning the exercise of parental responsibility, whether through discussion and agreement between the parents or by application to the court and the court having reached a decision based on welfare, it is incumbent on the parents to assist and support the girls with the consequences of that decision. It is not a reason not to make that decision, if it is considered in the girls' interests to do so.
"Obviously in reaching this decision I am aware this is against the girls' wishes, but that is not the only factor. It is of course an important factor, particularly bearing in mind their ages but the court also has to consider their level of understanding of the issues involved and what factors have influenced their views. In this case I do not consider there is a balanced level of understanding by them of the issues involved."
She went on: "The medical advice is for children to receive the vaccine even though it is accepted there are risks of side effects of the vaccine. The health risk of getting any of the diseases the vaccine prevents is clear. They are serious diseases that could have long term health consequences."
Liberal Democrat MP John Hemming, who represents Birmingham Yardley and chairs the campaign group Justice for Families, said delay in producing judgements is a issue in family courts and that Mrs Justice Theis should have published the MMR ruling earlier.
"The delay in producing family court judgements following private hearings deeply concerns me and this is par for the course," said Mr Hemming.
"You cannot blame parties involved for risking being in contempt by letting journalists know when decisions like this have been made. But without the judgement, we don't know the reasons, the arguments, and people can't have an informed debate.
"MMR is an important issue - although it's not the first time it's come before the courts. There is no doubt in this case that the judge should have issued an anonymised judgement at an early stage."
The public are generally barred from hearings in the Family Division and cases are listed only by number, although journalists have a right to attend.
Judges' rulings are usually published on a legal website with parties' made anonymous.
Last month Sir James Munby, president of the Family Division of the High Court - and the most senior family judge in England and Wales - said there is a "pressing need" for more transparency in family courts.