University of AucklandMonday 13 August 2012, 2:12PM
Media release from University of Auckland
Research from The University of Auckland, published in this month's
issue of The Australian and New Zealand Journal of Public Health,
shows a 20 percent reduction in the New Zealand hospital admission
rates for whooping cough (pertussis) in the 2000s compared with the
Associate Professor Cameron Grant from the University's Department
of Paediatrics, Growing Up in New Zealand and Starship Children's
Hospital says the 2000s was the first decade since the 1960s that
the whooping cough hospitalization rate had decreased rather than
"The reduction coincides with a clear and focused national strategy
to raise immunisation coverage levels in babies and young
children," he says. "Improving immunisation coverage has been one
of the National Health Targets since these were first introduced in
2007. The reduction in hospitalisation rates affirms the value of
this strategy and gives all of those working in the area of vaccine
delivery confidence, knowing that what they are doing is proving
effective in reducing the number of little babies in hospital with
this horrible disease."
"Young babies are exquisitely vulnerable to this disease", says Dr
Grant. "Most who die from whooping cough are under two months
A child who catches whooping cough when less than one year old has
a 60 percent chance of requiring hospital admission. Of those
infants admitted to hospital with whooping cough, one in ten will
need intensive care. Each of those infants in intensive care has a
one-in-six chance of dying or being left with permanent brain or
lung damage as a direct result of whooping cough.
Incomplete immunisation has been the main reason for New Zealand's
excessive whooping cough disease burden. The whooping cough
hospitalisation rate is now three times higher than that for
Australia or the United States. In the 1990s it was six times
higher than in the United States.
For the first 15 years after 1945, when pertussis vaccine was
introduced into New Zealand, the whooping cough hospitalisation
rate fell. However in the following decades, hospital admissions
increased steadily with the hospital admission rate in the 1990s
being more than twice as high as it had been in the 1960s. A
national immunisation survey in 1992 showed that only 60 percent of
children had received all of their scheduled immunisations by age
The immunisation coverage targets that were set were for 85 percent
of two-year-olds to be fully immunised by July 2010; 90 percent by
July 2011; and 95 percent by July 2012. As of June 2012 93 percent
of New Zealand children had received all of their scheduled doses
of whooping cough vaccine.
The reduced rate of hospitalisation is very exciting, says Dr
Grant. However, to further reduce the burden of this severe
disease, immunisation coverage will need to be sustained at high
levels over many years. Until that is achieved we will continue to
experience epidemics of whooping cough such as the one currently
gripping the country.
Also the immunisations need to be delivered on time. At present one
in four New Zealand infants are at increased risk of ending up in
hospital with whooping cough because their six week, three month or
five month immunisations are delayed.
Whooping cough is a highly infectious disease, he explains, with
every case causing more than 15 others. It is more than twice as
infectious as influenza. Babies acquire very little protection
through antibody crossover from the placenta or from breast milk.
Those who get whooping cough do not necessarily acquire immunity
through having the disease. Many people have it more than once in
"Having shown that we can improve immunisation coverage we must now
shift our focus to delivering immunisations on time" say Dr. Grant.
Understanding how best to do this is one of the areas of focus of
Growing Up in New Zealand, New Zealand's new birth cohort
"Immunisation decision-making by both mothers and fathers starts
during pregnancy. Getting immunisations on time requires good
relationships between families and health care providers."
"Growing Up in New Zealand is ideally placed to help us know how to
make further improvements in immunisation delivery. Of studies in
New Zealand it is unique in that it has enrolled both parents,
started during the pregnancy, and has maintained contact with 95
percent of the 6,846 children enrolled. Because Growing Up in New
Zealand was able to enrol a socioeconomically and ethnically
diverse sample it will be able to find answers to this and other
important child health questions for children and families from all
walks of life."