The mother does not want him to have the MMR (which protects against measles, mumps and rubella) and 4-in-1 (diphtheria, whooping cough, polio and tetanus) booster shots -- while the father does.
A High Court judge yesterday said he could not give a "snap judgment" in favour or against the injections.
Mr Justice Michael Moriarty directed the Attorney General be served with notice of the proceedings because of the constitutional arguments which arise in the case.
Mr Justice Moriarty has already heard evidence from the mother of the child who does not want her son to have the vaccinations and the father who wants the injections to be given as speedily as possible.
The judge said this unfortunate but undoubtedly significant matter related to vehemently opposing positions taken by the estranged parents of the child who was due to get his two booster shots last February.
The District Court and Circuit Court have already ruled the inoculations should proceed, in accordance with the father's wishes.
The case was before the High Court as a result of a legal challenge mounted by the mother.
Outlining the background to the case, Mr Justice Moriarty said after the child was born in 2007 he was immunised without dispute and no adverse reactions were reported after any of the shots. The parents' relationship later broke down.
Last February, the child was due to receive the two injections provided for under the HSE programme to children in Junior Infants but the judge said the differences between the parents had extended to the desirability and safety of those procedures.
The mother had concerns about the substances included in the injections and was reluctant to accept, what seemed to her, blind faith on the part of local doctors that the procedures were favourable to her son.
An impasse was rapidly reached and the District Court ruled that it was in the best interests of the child that the injections go ahead, Mr Justice Moriarty said.
The mother appealed the matter to the Circuit Court where the judge there, after "a careful and considered hearing", decided the injections were in the child's best interests. On the day the vaccination was to be administered the mother applied to the High Court to be allowed legally challenge the decision of the Circuit Court.
Mr Justice Moriarty said the father in evidence had indicated although he felt strongly his son should have the injections, he would accept a verdict contrary to his wishes from the court without seeking to take matters further.
He also acknowledged that the child's mother, like him, was a caring parent and wanted only what was best for him.
The judge said the more he examined the matters the more apparent it was that he could not "simply furnish some form of snap judgment in favour of or against the injections".
"I am acutely conscious of the delay factor, and can only give my best assurance to the parties that I will do all possible on my part to expedite a just conclusion," the judge added.