National clinical director of health protection Dr Susan Jack says New Zealand is on high alert for an outbreak.
There were 187 whooping cough cases reported in September, some of the highest levels recorded since early 2019.
It is more than double the 75 cases reported in August.
"We typically see whooping cough outbreaks every three to five years. Covid has disrupted that pattern, but it's actually been six years since our last outbreak in New Zealand," Dr Jack said.
"And also noting there are high numbers in Australia and other parts of the world, we've now reached a level where we think we're on the cusp of a national outbreak, so we're asking people to take action now."
Dr Jack said newborn babies were of most concern, and urged pregnant people and others at risk to get vaccinated.
"You can get vaccinated from 16 weeks on in your pregnancy, and this will protect your newborn baby who are too young to be vaccinated, when they're most at risk of whooping cough."
Dr Jack said low rates of vaccination were driving the risk of transmission.
"Our vaccination rates have been lower than what we hope for. So this is a request for people to check their vaccination records and those of their children and get up to date, it's never too late to get up to date on your vaccinations."
Alerts have been sent to practitioners, encouraging them to stay vigilant for signs of whooping cough.
Signs of whooping cough were like other respiratory infections, Dr Jack said, before the cough started.
"For babies and for especially young babies, they might not have that 'whoop', they might just have a sight cough, but they might stop breathing and turn blue, and it can very serious and dangerous for young babies."
Vaccinations are free for all children under 18, and for those over 65.
