Meningitis killed five children last month, prompting fears the $220 million Government vaccination campaign against the MeNZB epidemic strain has failed to deliver as promised.

The latest monthly death toll is the highest in nine years.

Anti-vaccination campaigners said analysis of Ministry of Health figures showed that north of the Bombay Hills, the vaccine for the epidemic strain, given to more than one million children, had an efficacy, or effectiveness, rate of only 9 per cent.

The data showed that for the six months to May 2006, there had been proportionately as many cases of the epidemic strain of the meningococcal disease in fully vaccinated children (1.1 per 100,000) as there had been in partially vaccinated and unvaccinated children (1.2 per 100,000).

Ministry of Health authorities rubbished the claims, and said that parents who immunised their children could have complete faith in the vaccine, which they said was 80 per cent effective.

There were 35 cases of meningococcal disease in July, 16 of them in greater Auckland, which was the highest monthly total since before children started getting their third vaccine dose. Five deaths is the highest monthly tally since June 1997.

Using the formula the ministry proposed before the vaccine was rolled out, the effectiveness for the past six months is only 9 per cent. However, officials have discarded this in favour of a statistical model which showed an efficacy rate of 80 per cent since the campaign began in 2004.

Ron Law, a risk and policy analyst and former ministry consultant, is calling for a Royal Commission of Inquiry into what he called "the manipulation of science to justify a medical experiment involving more than one million children". He said if the vaccine was 80 per cent effective, the number of unvaccinated children with the disease would be far higher.

In the six months to May, there were five cases of the epidemic strain in under-20-year-olds in the Counties Manukau, Auckland, Waitemata and Northland district health board areas - the most high-risk areas targeted by the vaccination campaign.

Only 81,030 children in the northern region were unvaccinated; 438,000 had received all three jabs. Four of the children with the disease were fully vaccinated and one was unvaccinated, which Law said showed the vaccine was not having the promised effect.

Dr Jane O'Hallahan, head of the Government's meningococcal B programme, acknowledged the accuracy of the data, but dismissed Law's analysis as "science fiction".

Instead, she pointed to an international expert panel peer review which said the vaccine had an 80 per cent efficacy. She said the study showed unvaccinated children were five times more likely to develop the disease.

"It's not 100 per cent effective, no vaccine is, but it's the best we've got. There is no room for complacency, the strain is still in New Zealand and looking for vulnerable hosts."