Expert warns whooping cough outbreak due, more likely once borders open

New Zealand is due for an outbreak of a disease three times as infectious as Omicron, an expert has warned, with the almost two-year border closure likely to make it worse than previous waves. 

While next year's planned reopening has been thrown into doubt following the emergence of Omicron, when it eventually does happen whooping cough is likely to make a roaring comeback, says Helen Petousis-Harris, vaccinologist and head of the University of Auckland's Vaccine Datalink Research Group.

"The high level of isolation we’ve experienced will make us more vulnerable to contracting diseases such as pertussis once they are in circulation as we accumulate susceptible people," she said on Thursday, using an alternative name for the disease.

"We saw this with the outbreak of RSV with many not yet having developed or maintained immunity due to a lack of exposure to common respiratory viruses."

Whooping cough is caused by a bacteria, Bordetella pertussis. It can cause pneumonia, seizures, brain damage, deafness, blindness and even death, particularly in infants. The cough can persists for months after the initial infection is cleared. Half of all babies under one year old need hospital treatment, according to Health Navigator, and of those one or two will die. 

Each person who's infected spreads it to between five and 17 others on average. There is a vaccine, delivered in five doses through childhood - three in infancy and two boosters, at ages four and 11. Adult boosters are also available at ages 45 and 65, as well as for pregnant mothers - all are free. 

But Dr Petousis-Harris says health officials have "seen declines in vaccine uptake which could compound the problem". 

The last whooping cough outbreak started in 2017 and saw more than 4600 Kiwis infected over the course of a couple of years. Thankfully none died. The previous outbreak started in 2012, leaving three dead - two babies under six weeks old, so too young for vaccinations, and an unimmunised pre-schooler.

Helen Petousis-Harris.
Helen Petousis-Harris. Photo credit: The AM Show

Dr Petousis-Harris is currently leading a study into whooping cough's effects on adults, who usually suffer a milder illness than children and can sometimes go unreported. She says the research will help protect the wider population against outbreaks. 

"Developing national epidemiological data creates better understanding, raises awareness and allows for the creation of targeted health interventions - helping us protect our most vulnerable from this potentially devastating disease… My suggestion is that Kiwis check the vaccine status of their whole family, it is easy to let this slip in the middle of a pandemic."