Hello advice please

Well i have my duck choice down to saxonys or appleyards. I have also decided to extent there run space to 12x6 giving them plenty of space. One question reference chickens the place i am looking to get them from says they are vaccinated. What are they vaccinated against and is this general practice when selling poultry?

We used to have two Khaki Campbells, they were very friendly (one a lot more so) and laid plenty of eggs.  They had a house on stilts with a gangway up to it and a fenced off area of garden about 3 metres by 6 metres, with areas of grass and mud and a small area of water.  They loved woodlice to eat.  My neighbours used to say they loved their gentle mooching noises but they knew when we came home as the ducks would shout their heads off   My OH used to have an Aylsbury duck brilliant white!  Each time he came home the duck would quack and quack till he went out and fussed him awwww.