The Northland District Health Board is advising people to be vaccinated against the deadly whooping cough following 36 confirmed or probable cases reported in the region so far this year.
Those most at risk are infants under 12 months of age who are five times more likely to be hospitalised with whooping cough than babies who received on-time doses of pertussis-containing vaccine.
From the beginning of this year until Tuesday, 36 confirmed or probable cases have been reported in Northland compared with 48 for the same period last year.
Of that number, four were admitted to and recovered in hospitals throughout Northland.
Northland DHB Medical Officer for Health, Dr Jose Ortega Benito, said women from week 28 of their pregnancy could get Boostrix as it was funded and prevented the baby from catching the infection
On-time immunisations for the infant at six weeks, three months, five months and further protection was available with booster vaccines at four years and 11 years of age, he said.
"There is not an identifiable outbreak in Northland, but a national one that also affects our region, although to lesser extents and clearly decreasing in numbers," Dr Benito said.
"People should see their GPs if they develop symptoms to check on the appropriate immunisation vaccines and to have themselves vaccinated.
"In winter months when the temperatures are low, humidity is high, the immune systems go down, houses are damp and cold are when respiratory diseases like whooping cough are prevalent."
Antibiotics, such as erythromycin, can be prescribed during the early stages to reduce spread of the disease.
Dr Benito said whooping cough was an infectious disease that can cause serious complications such as coughing, choking, breathing difficulties, pneumonia and seizures.
The bacteria are easily spread by coughing and sneezing.
During September and October 2017, there were 22 lab confirmed cases of whooping cough linked to Ngunguru School where most patients were unimmunised or partially immunised.