Like the fluoride-in-water debate and whether Christian Cullen deserves another shot in the All Blacks, some issues just don't go away.

The long-running and fiercely divisive debate about immunisation has erupted again with Public Health director Colin Tukuitonga warning midwives, in many instances the lead maternity carers, they could be endangering the lives of babies if they provide parents or caregivers with information pamphlets published by the Immunisation Awareness Society.

He further said he was seeking legal opinion on whether midwives who did not promote immunisation were breaching their contracts with the Ministry of Health.

Among the points in the IAS pamphlet are those which say vaccinations are not effective in preventing or combating diseases.

The leaflets, written in plain English and with reference to research papers and medical texts, have been handed out to some new parents by well-intentioned midwives to allow them to consider all aspects of the immunisation debate and make an informed decision.

However, Dr Nikki Turner, director of the Immunisation Advisory Centre, says the IAS pamphlet is confusing and "wildly inaccurate" and this week the IAC, published its own point-by-point critique of the pamphlet.

For parents of newborn babies all this could be worrying and confusing, not the least because the names of the two organisations at loggerheads are so similar. The IAC is a research organisation based at the University of Auckland and promotes immunisation. The IAS is a voluntary organisation relying on subscriptions and donations and counsels caution. Both have thorough websites, the IAC with documents and material supporting vaccination programmes, the IAS with links to international pro-choice sites.

"To me the picture is simple," says Hilary Butler, founder of IAS and author of the controversial pamphlet. "Parents should be given all the information and be allowed to make their own choice."

And many parents may feel, as a letter writer to this paper said this week, that they are mature, educated and capable of making their own decisions after reading and deliberating on the available information.

But much of that information is conflicting and, as well-mannered accusations flew from the pro-immunisation side ("misleading and unfortunate", was how Tukuitonga described the IAS pamphlet), it is not an easy issue for unhappy parents to resolve.

Turner insists this is not a midwife-bashing campaign but says there is a need for all health professionals to be critical of their data and positions, including pro-immunisation doctors.

But, she says, while "science isn't always accurate, science is based on something which is more than anecdote and personal opinion".

The IAC critique of the IAS pamphlet is headed by a quote from essayist James Schlessinger: "Everyone is entitled to their own opinions, but no one is entitled to their own facts."

Quite why the immunisation debate has come up again is interesting, especially since the IAS pamphlet has been around for at least two years. Butler says it is a result of the conviction of the Moorheads, whose six-month-old son Caleb died of bronchia-pneumonia. The religious couple who observed a vegan diet and relied strictly on herbal remedies were found guilty of failing in their duty as parents to provide him with the necessaries of life.

"We've had a court case," says Butler, "where public opinion says parents who don't do the right thing for their children should be taken to court and put in jail. [The IAC] is tailgating on public outrage about parents who didn't do something they should have done and their child dies as a result ... so now they are extrapolating that to parents who don't do something they should do, like immunisation, saying they should be taken to court and be put away. They could have raised this 18 months ago. Why didn't they?"

For parents, access to both sides of the immunisation issue is relatively easy in this wired world.

But even the well-educated would grapple with an entry such as this on the IAS website: "Despite these promising indications from experimental models, the immunological mechanisms required to engender resistance have been defined in very few infectious diseases of man and domestic animals ... In some cases, the humoral response following vaccination may be detrimental to host resistance, and exacerbation of disease may occur following challenge." That's from Modern Vaccinology by Edouard Kurstak, printed in 1994.

On the other side of the discussion, the eight-page paper on the IAC site about the MMR vaccine and links with autism is considered "one of the most readable summaries of research to date". Well, if you are a doctor, perhaps. Laypeople would approach the perilous piles of polysyllables with trepidation.

Most parents do have their children vaccinated, but there is also a lot of fear among those who hear anecdotal evidence of kids becoming sick after immunisation.

Then there are perceptions of an uncompromising agenda pursued by the medical profession and the sense that parental choice is being denied by doctors. In a world where many believe personal freedoms are being eroded by forces beyond their control, here is an area in which some feel they can make a stand.

The anti-immunisation lobby can also adopt the moral position that their objection is founded on what is good for the family.

The IAS website has logged more than 10,000 hits and some of the documentation provided makes persuasive reading.

For example, the research paper presented to the British Thoracic Society meeting in December 1997 involved a study of almost 2000 patients at an Oxfordshire GP practice born between 1975 and 1984. The paper said children vaccinated against whooping cough were 50 per cent more likely to develop asthma, eczema and hay fever in later life. It also said being given antibiotics as a baby puts children at three times greater risk of developing allergic diseases, and supported some doctors' claims there was a link between mass vaccination against whooping cough in infants and an explosion in the number of childhood asthma cases.

Parents reading only that might feel justified in immediately pulling their children out of vaccinations programmes for whooping cough.

"In Australia," Butler adds, "they have had a full immunisation rate for whooping cough of 92 per cent. Their epidemic started in '93 and it's still going rampant, despite that immunisation rate. It's a joke."

But we live in a world where things are not quite so clear-cut

Helen Petousis-Harris, a researcher at IAC, can immediately present an academic paper by the International Study for Asthma Allergy Collaboration (ISAAC) which found there was no association between immunisation and the development of allergies. She also says the research paper on the IAS website is, as far as she can find, not published data and therefore has not had peer review.

"And something that profound would cause a lot of interest."

As to the whooping cough epidemic in Australia, Petousis-Harris says, "Well, the Aussies don't know they've got an epidemic. I've got their 2002 communicable disease intelligence report and they say, 'no epidemic occurred in '99-'00' and they are not experiencing an epidemic at the moment."

Between claim and counter-claim it would seem the only place for solace would be in statistics which should be bold and bare enough. However, even here there is confusion.

Earlier this month, when the Ministry of Health announced it was developing a national vaccinations database, Claire Mills, manager of the immunisation programme, said we weren't doing well in relation to other developing countries.

She cited a mid-90s survey in Northland which showed a 65 per cent coverage for Pakeha children and 46 per cent for Maori. Figures from Australia, which has had a national register since 1996, last year showed 94 per cent coverage for children aged one year. In that light, our statistics, if you back immunisation, look grim.

Commissioner for Children Roger McClay also weighed in when he said immunisation rates were sometimes down in the 70s and 80s, percentage-wise, when they should be in the 90s.

However, the use of an old regional survey of one of the poorest parts of the country invites an invalid comparison, and McClay's lack of specifics was unhelpful.

Then, this week, Sandy Grey, national president of the College of Midwives, noted that while it was a concern if children weren't part of the programme, "in fact, 94 per cent of babies are immunised at six weeks, so the actual feed-in to the immunisation programme is exceedingly effective".

And, on the face of it, that's as good as across the Tasman. Or maybe not.

Put bluntly, we don't really know what immunisation levels we have, as no recent figures are available.

"I wouldn't trust any data at the moment," says the IAC's Turner, "but what we do know is we've just come out of a whooping cough epidemic so we know our rates aren't great."

And because immunisation involves a series of injections, if we start low we can expect return rates to drop, sometimes by 20 to 30 per cent. So even if we did hit 94 per cent of all babies at six months - which most health professionals would consider a very generous figure - then we could expect declining rates thereafter. Parents who are ambivalent about immunisation may let their kids get the first jab, but won't follow through for subsequent ones.

The subtext of some objections to immunisation is suspicion, says Turner.

"It's not about your personal relationship with your health professional because when people look at research on relationships with GPs, for example, it's very trusting. What people are suspicious of is government, pharmaceutical companies, big money and big business, and that we're just the small guys.

"What comes through is people don't believe government pamphlets and don't tend to believe governments. We think they are making big decisions which are outside our control. I can understand that; I feel that, too.

"But on a personal level if you have a good relationship with your health professional then you can talk through the issues."

Turner takes a long view but also puts the microscope on the consequences of people opting out of immunisation programmes.

"You can't snack on health care and say you won't take the vaccine but that when your child gets sick and is on a ventilator you want all the tertiary medical services on offer. You have to be consistent."

The most recent report from the Ministry of Health issued last year and based on 1998 puts the number of babies immunised at six weeks at 82 per cent, compared with 92 per cent for 1996.