"The mistake that we made was that we underestimated the diseases and we totally over-estimated the adverse reactions", says father Ian Williams, who is speaking publicly of his family's ordeal in an effort to warn other parents about the dangers of not immunising their children.

Minor cut, major infection

It started when seven-year-old Alijah got a small cut on the bottom of his foot in December 2012.

"Of course we didn't think it was too serious, it was just a little cut but a couple of days later he started getting symptoms like a stroke on the side of his face," Mr Williams says.

"A couple of days later during the night he started to get cramps across his face. His face would contort and he was in a lot of pain."

After 24 hours in Auckland's Starship Children's hospital, the doctors diagnosed Alijah with tetanus, and he was taken to intensive care.

Mr Williams recalls his son's agony, "It's a terrible thing... Your whole body arches, your arms go up in the air."

"It's like getting cramp but it's everywhere, across the face as well. They are so tight your jaw locks."