We have just got a letter to say that dd (13m)needs a Hib booster. This will be the 4th vaccinne against Hib. Reading between the lines of the official leaflet, it appears the vaccinne used recently in the DTPHib injections was not effective enough, so they want to do everyone again in case they aren't covered. I am a bit loath to give dd yet another vaccine, just in case she was unlucky and the last 3 didn't work. Has anybody else been told they need this? Are there tests to check whether she is immunised or not?