West Coast Medical Officer of Health Dr Cheryl Brunton said the very young were the most vulnerable to becoming seriously ill.
"We are asking those who most commonly come into contact with this vulnerable group to protect them by having the booster vaccine themselves."
The booster vaccine was also available for other adults who felt they might need it, but they would have to pay.
Whooping cough immunity wanes with age, so older people can contract it and pass it on to others even if they have been immunised or had the disease as a child.
Dr Brunton urged parents to keep children home from school or preschool and to stay at home from work themselves, if they developed a persistent cough.
"The incubation period for pertussis ranges from 5-21 days. So if someone goes to work, school or pre-school with a persistent cough, by the time they find out they have pertussis the damage has probably been done as far as spreading it to other children and workmates."
She would contact schools and early childhood centres outside the Westland district, to advise them of the precautions they should take next term, she said.