The Ministry of Heath has declared a national outbreak of whooping cough.
In 2017, there had been 1315 cases, of which about 200 were in Otago and Southland.
Ministry of Health public health director Dr Caroline McElnay said babies under 1-year-old were most vulnerable.
"The best way to protect babies is for pregnant women to get their free immunisation against whooping cough between 28 and 38 weeks of pregnancy, and take their baby for their free immunisations when they’re 6 weeks, 3 months, and 5 months old.
"Any siblings should also be up-to-date with their immunisations, older children receive free boosters at 4 and 11 years of age.
"If people are unsure whether they or their children have been immunised, they can talk to their health practitioner, doctor or nurse," Dr McElnay said.
Pregnant women who were vaccinated passed their immunity on to their babies, protecting them until they could be immunised at six weeks. People were asked to be "vigilant" at Christmas and New Year celebrations.
"Anyone with coughs should be especially careful if they are likely to come in to contact with babies.
"Most adults don’t realise they have whooping cough, but it is incredibly contagious," Dr McElnay said.
Outbreaks of the disease occurred every three to five years, most recently from August 2011 to December 2013 when 11,000 cases were notified.
