In the last whooping cough epidemic, in 2018, there were four deaths in total, he said.
“Just to have it happen so suddenly, such a tragic start to this current epidemic, is heart-wrenching,” he said.
The disease, also known as pertussis, was particularly dangerous for children, he said.
“Pertussis is a disease we hate. Once a child gets it there is nothing we can do about it. We just have to watch, almost helplessly, as a child can often cough themselves to be very sick.”
Whooping cough epidemics tended to occur every four or five years. Cases had been low during the Covid-19 epidemic but were picking up, he said.
There had been eight cases notified in 2023, all but one of them children, and three children hospitalised.
Sinclair said there were likely to have been more cases, and the number was expected to rise over the next year to 18 months.
Since the last outbreak, in 2018, childhood immunisation rates have declined from 78 per cent to 69 per cent.
The rate was much worse for Māori children, down from 61 per cent to 49 per cent.
The fall was setting the stage for a worse epidemic than the one in 2013 where about 2000 children under one caught the disease over a two-year period, Sinclair said.
In communities with low immunisation rates, the disease would spread faster, meaning Māori communities were more at risk.
He urged everyone to check their baby was up to date with their vaccinations.
Whānau expecting a baby should also make sure adults and older children were vaccinated as they could pass it on to children, even if they have mild symptoms.
Sinclair wanted better communication from health authorities about the danger of the disease and the importance of being immunised, saying any messages so far had lacked intensity.