Canterbury health officials are investigating a possible failure of the measles vaccine after an outbreak in immunised teenagers.
Canterbury medical officer of health Dr Ramon Pink said yesterday there were 21 confirmed cases of measles in the region.
Six of the patients had been fully vaccinated and three had been given one of the two jabs in a course to guard against measles, Pink said.
"The fact that some of the young people with measles have been immunised is concerning and work is being done to identify the batch numbers of the vaccine given to them. We do not yet know why it has been ineffective, but we will keep looking."
Health staff were reviewing vaccine batch numbers and investigating transportation and storage.
Vaccinations needed to be cooled and kept under particular conditions.
National guidelines were introduced several years ago but would not have been in place when most of the people involved in this measles outbreak were immunised.
Most cases in the outbreak were school students aged between 11 and 16; measles vaccination is usually done before a child turns two.
Of the 21 confirmed measles cases, half were from Christchurch Boys High School. There were now cases from other schools, Pink said.
The measles, mumps and rubella vaccine (MMR) was 95 per cent effective in giving life-long immunity.
It was important parents immunised their children against measles, which could be serious, Pink said.
"All caregivers, particularly those concerned that their children could be at risk in this outbreak should check their children's immunisation record and if they have not been immunised contact their GP and arrange for it to be done."
Nikki Turner, of the Government-funded Immunisation Advisory Centre, said no vaccine was 100 per cent effective. Some people's bodies did not use the vaccine to build resistance, she said.
About five to 10 per cent of people would not be immune after vaccination with the MMR vaccine.
But immunisation meant it was harder for the virus to survive and spread, Turner said.
Immunisation Awareness Society of New Zealand spokeswoman Michelle Rudgley said the Canterbury situation proved the ineffectiveness of vaccines.
Rudgley said parents had been deceived by the pro-vaccination lobby to believe immunisation was safe and could totally protect their children against diseases.
The situation in Canterbury showed vaccinations often did not last into adolescence.
- By KIM THOMAS, The Press
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