Health New Zealand said a nationally coordinated response was now in place following a meeting of health officials on Thursday.
In the past four weeks, there have been 263 cases of whooping cough (Pertussis) - the highest number of cases over a month to date for all of 2024, with previous spikes in May, June and July.
Director of Public Health Dr Nicholas Jones said a number of countries were reporting record levels of Pertussis, possibly due to lower infection rates during the Covid-19 pandemic.
As in previous epidemics, Māori and Pacific pēpi would be most affected, he said.
"Our main concern with this epidemic is the risk of severe illness among babies either too young to be immunised or whose immunisations are delayed. Our key objective is to protect pēpi through on time vaccination and immunisation during pregnancy.
"Even in countries with very high levels of immunisation, epidemics still occur every few years, but the numbers of babies who get very sick is much lower when mothers have been vaccinated during pregnancy, and when pēpi are vaccinated on time," Dr Jones said.
Te Whatu Ora national clinical director for protection Dr Susan Jack said the National Public Health Service was well prepared to manage the epidemic, with a national response team stood up to coordinate and support activity across public health services.
"Our last major outbreak of pertussis was in 2017, but they can last for months and potentially for a year or more, so this will be a marathon, not a sprint."
Whooping cough is particularly dangerous for newborn babies, and older adults, and in some cases it can be fatal, she said.
"Sadly, three babies died from whooping cough last year, and we want to avoid that happening again."
Around 50 percent of pēpi who catch whooping cough before the age of 12 months need hospitalisation and one or two in 100 of those hospitalised pēpi die from the infection.
"The best protection for infants is for their mother to be vaccinated during pregnancy. The antenatal vaccination for pertussis is safe and free. This is most effective when given from 16 weeks of pregnancy - and should be done during each pregnancy to provide the best protection for each baby," Dr Jack said.
Childhood vaccinations to protect against whooping cough are needed at ages six weeks, three months and five months, and again at four years.
A further booster is given at age 11 years (school year 7).
Vaccination is free for pregnant people.
Adults are eligible for one free booster from age 45 (if they have not had four previous tetanus doses) and can get one free from age 65.
Whooping cough causes breathing difficulties and severe coughing fits. The cough can go on for weeks or months which is why it is sometimes called the "100-day cough".
People are most infectious in the early stages - with the first signs of whooping cough usually appearing around 1 week after infection:
After about 1 week, symptoms include:
• a blocked or runny nose
• sneezing
• a mild fever
• coughing.
• uncontrollable coughing fits that last for a few minutes
• coughing that leads to vomiting
• a thick mucus that can make you vomit or choke
• during coughing spells, young babies may gasp for air and may briefly stop breathing and turn blue.
