WAKEUP CALL: Ian Williams says he and his wife’s reliance on "intuition and feelings" put their son Alijah at death’s door suffering from tetanus.

Ian Williams is a smart guy - a scientist, an inventor, a businessman - but when it came to son Alijah's health he dismissed science and behaved like a "hippy", creating a situation where Alijah almost died.

"Blood is dripping from his mouth and he is saying 'save me daddy'," Williams told the Sunday Star-Times.

"I was holding the hand of my kid who had an arched back, the muscles could break his bones at any second, and his heart could stop."

Alijah was hospitalised with tetanus late last year; something he should have been immunised against, something Williams and his wife Linda decided not to do.

It was a painful lesson. They watched as seven-year-old Alijah spent three weeks in hospital, his body violently and painfully convulsing as tetanus attacked his nervous system. "When it came to my kid's health, I let the hippy win. I should have let the science win."

And it's not as if Williams is unfamiliar with science. He has a science degree and he's turning his invention, the WilliamsWarne homebrew machine, into a global success.

He's not stupid. If anything, he was just a little bit too smart for his own good.

The Williams are the one in 10 parents who opt out when it comes to vaccination, not out of ignorance, but because they think they know everything. Williams said they believed they'd done their research but now admits they were out of their depth.

"Parents like us make the decision to not vaccinate on very little factual information about the actual consequences of the diseases."

He also says they fell for the myths and conspiracies that pepper the internet. The Williams downloaded information from the internet and underestimated the diseases while over-estimating the risks of the vaccine reactions. About one in one million will suffer a bad reaction to the tetanus vaccine - such as painful nerve inflammation - while Alijah had a one in 10 chance of dying from tetanus.

Alijah was discharged in a wheelchair on January 8 after 26 days in hospital. He faces a 12-month recovery including having to learn to eat and walk again.

Others have not been so lucky. A three-year-old unimmunised child died during the ongoing whooping cough epidemic last year. He should have been vaccinated by the time he was crawling.

Williams now wants Alijah to be a poster boy for immunisation, knowing his story will ignite fierce debate on the controversial issue.

They have immunised their other children and wrote to Alijah's school to warn parents who had not vaccinated.

Dr Nikki Turner, who heads the Immunisation Advisory Centre, said parents see a needle, the children's pain and hear scare stories.

"It's hard for a parent to think logically. If somebody is injecting a foreign substance in your kid's leg it's the fear of the unknown and a fear of conspiracy theories."

Those conspiracy theories are more infectious than ever as stories spread online.

New Zealand has its own anti-vaccine group, The Immunisation Awareness Society, which recently lost its charity status after the Charities Registration Board determined IAS did not actually "educate" parents and instead promoted a view that vaccination was "ineffective and dangerous" and that it sought to change government policy, which was a "political" purpose not a charitable one.

The group's website says it offers parents information to make an informed decision and has an article entitled "101 reasons to not vaccinate".

The lead story on its page on Friday read: "I am seeing a very disturbing trend occurring more frequently among pro-vaccination groups - and that is the belief that it is OK for some children to die from vaccine reactions, so that others may be ‘saved' by vaccines. If part of the risk of vaccination is that some might die, then that is simply not good enough. What ever happened to 'First do no harm?"'

The society was not available to talk last week.

"We've never had a death in New Zealand from a vaccination," Turner says.

Yes, children have died after being immunised. However, the deaths have always been linked to unrelated causes such as cot death.

"The early vaccines were less pure, they were more unsafe, there were deaths from smallpox vaccines."

Modern science and research has evolved and is far superior today, she says.

Williams tells parents to watch a video of a child suffering tetanus or whooping cough when making their decision on vaccinations.

He did not realise the severity of tetanus until his son went through it.

"We sat down and said 'f...ing hippies', because we were hippies about it. We used our intuition and feelings but there's no place for it. There's just statistics on disease and adverse reactions."

Alijah screamed in agony as he suffered spasms until doctors put him into an induced coma and on life support.

His mother, Linda Williams, wipes away tears as she talks about the past month. "It's been the worst nightmare ever, just horrible for everyone," she said. "If we can save just one child going through this then my task is done."

Already friends have vaccinated their children as a result of their story.

New Zealand had ranked near the bottom of developed nations for immunisation levels in the past, but in the past five years we've shot towards to the top.

Previous low immunisation levels have contributed to an outbreak of whooping cough.

The highly infectious bacterial infection killed two children, hospitalised hundreds and infected almost 6000 people last year.

The Government recently introduced a goal of having 95 per cent of eight-month-old children fully immunised by the end of 2014, including protection against whooping cough, polio and tetanus.

The current rate is 87 per cent, and as low as 75 per cent in Northland.

Dr Julia Peters, clinical director of the Auckland Regional Public Health Service, said young children are most at risk from whooping cough, which causes severe coughing and can lead to pneumonia, brain damage, convulsions and death in infants.

"That's why it's so important they are immunised. The more people immunised - it's like a social contract - the more protected our society is as a whole.

"Immunisation is extremely safe. It is incredibly easy to protect your own child and society."