Polio is a dreadful disease, but bring up the subject of immunisation and Harold Kipchumba leans heavily forward on his crutches and animatedly holds court on the subject.
But behind the relaxed and convivial façade lies a woeful tale of tears, love and pain that the family of Kipchumba, the UN Immunisation Goodwill Ambassador, has had to endure for the past five years, after a road accident in 2013.