Thousands fall into inoculation gap

Thousands of Auckland teenagers and young adults are likely to be at risk of catching measles because vaccination rates were so low when they were babies.

Auckland Regional Public Health Service (ARPHS) medical officer of health Dr William Rainger has warned that those aged between 13 and 29 are one of the groups most affected by Auckland’s measles outbreak.

The Herald has calculated from immunisation records that each year from 1992 to 2010 in Auckland alone more than 5000 2-year-olds were not vaccinated against measles, and in 1992 it was probably many more.

Health experts say that although there will have been some catch-up, there has been no formal campaign to raise the immunity of today’s young adult population.

New Zealand children receive two measles vaccinations; the first at 15 months and the second at 4 years.

A National Immunisation Register was created in 2005. Before that, immunisation levels were estimated based on vaccination claims from general practitioners and infrequent national coverage surveys.

Records from the immunisation register show that in 2009, the first year data is available, only 77 per cent of those who turned 2 in Auckland were fully vaccinated. That means 5517 young children in that year were not fully vaccinated.

The Herald has calculated how many were not fully immunised at age 2 in Auckland in 2009.

This data suggests although most current measles cases are in Counties Manukau, there is still an immunity gap in the rest of Auckland.

Dr Nikki Turner, the director of the Immunisation Advisory Centre, says the size of the immunisation gaps is unknown, and even if many people received catch-ups, a lot would still have missed out.

Blood tests for immunity are also used to estimate immunisation gaps but Turner says they don’t give any extra data and they suggest that 20 to 30 per cent of the young adult population might not be immune to measles.

Turner’s research shows the 2009 2-year-olds are likely the best protected of today’s 13- to 29-yearolds.

In 1992, 2-year-old vaccination coverage may have been below 60 per cent, meaning almost 10,000 Auckland infants weren’t fully vaccinated at that age.

Low vaccination rates have been blamed on the anti-immunisation movement. But Turner said many people didn’t get their children vaccinated for other reasons, such as difficulty accessing health services.