My DS is due for next set of booster jabs, he is 3.6yrs. It is his MMR booster, Polio booster and Hib. Can anyone tell me why we have Polio anymore and what is the Hib one for? Are they really needed? I am not being thick or stubborn about any of these things i just wanted to know exactly what and why the last two were still given. Thanks if anyone can help me out.