Northland health officials are advising pregnant women to get their free immunisation against whooping cough between 28 and 38 weeks of pregnancy, which will pass immunity to their unborn babies.
Northland District Health Board spokesman Dr Jose Ortega Benito said babies under 1-year-old were most vulnerable to the highly contagious disease. Babies can have free jabs at 6 weeks, 3 months and 5 months old. Any siblings should be up-to-date with their free boosters, given at 4 and 11 years of age.
Babies with whooping cough often have trouble feeding and breathing.
Symptoms include intense bouts of coughing, which bring up thick phlegm; a "whoop" sound with each sharp intake of breath after coughing; vomiting after coughing, especially in infants and young children; and redness in the face from the effort of coughing.
The previous outbreak began in August 2011, peaking in December 2013, with about 11,000 cases. Three young children died from the disease in that period.