Six cases of whooping cough have been confirmed in Central Otago - five of them in children.
The Southern District Health Board said the cases were in Wanaka and Hawea, and a further six were probable.
It said it had been notified of more than 80 possible cases in those areas so far, plus two in Cromwell and four in Queenstown.
Director of the Immunisation Advisory Centre, Nikki Turner, reminded people of the value of vaccination against whooping cough, or pertussis.
"We need to be very sure that all the children are immunised, and immunised on time, and pregnant mothers immunised to protect their new-born infants," she said.