By a journey to Ireland on less than 1 month recommend protection against the following infections:
Diphtheria Diphtheria is a serious throat infection, which infects from person-to-person through the air. The vaccination should be less than 10 years old otherwise a booster is needed. Read more about diphteria here.
Tetanus Tetanus is a complication to wounds contaminated by soil. If there has been a vaccination within the past 10 years it is not necessary to give a booster in case of wounds and accidents. Tetanus vaccinations are usually given in combination with diphtheria vaccine. If you are previously vaccinated, the vaccine can be given right up to departure.