Why we immunise

Helen Petousis-Harris from the Immunisation Advisory Centre says: "Immunisation may be undervalued by virtue of its own success." What she means is that common childhood illnesses of the past are now rare thanks to vaccines. We've forgotten the damage these illnesses caused.

International experience tells us that infectious diseases can return in the absence of vaccines. In Japan, immunisation against whooping cough dropped around the mid-1970s. The number of whooping cough cases jumped from 393 cases and no deaths in 1974 to 13,000 cases and 41 deaths in 1979. Similar experiences occurred in Sweden and Great Britain.

To stop disease outbreaks, immunisation programmes must sustain rates of between 85 and 95 percent. Only 79 percent of Kiwi one-year-olds are immunised against measles (it's at 94 percent in Australia and 93 percent in the US). The Immunisation Advisory Centre is surprised that we haven't had a measles epidemic yet.

Economic evaluation

Critics argue that we invest too much faith and money in vaccinations. Chiropractor Tat Loo (pictured) says "Giving out a new vaccination appears to be more newsworthy, more important, and easier to spend public money on than more serious (though prosaic) health issues like New Zealand children not eating enough fruit and vegetables."

Dr Richard Milne is an Honorary Associate Professor at the University of Auckland and a private consultant in economic evaluation. He says immunisation programmes are subjected to more rigorous economic evaluation than most other forms of government investment in health.

"We ask questions such as: 'what will the programme cost the government and families? What health benefits will it deliver, and how soon? Does it provide good value for money compared with other expenditure on healthcare?'" The findings of this type of evaluation help the government to set priorities for its expenditure on public health.

For example, the government considered six new vaccines in 2007, but only two of these were subsequently included on the National Immunisation Schedule. The decision to fund these two vaccines, but not the other four, was based partly on economic evaluations.