You do not need any vaccinations in order to visit the Maldives, and the biggest risk to health is from sunburn and failure to decompress properly while diving.
There is no reciprocal healthcare agreement between the UK and The Maldives to provide Medical treatment, and you should be aware that there are only two hospitals in the country, which are both very expensive to use.
It is therefore vitally important to take out comprehensive medical insurance prior to travelling to The Maldives that will provide cover for treatment and medical evacuation back to the UK or to a more developed country such as the UAE if necessary.