Two people have died from whooping cough, health officials say, and there are concerns about the further spread of the disease because of low vaccination rates.

Te Whatu Ora/Health NZ announced the “tragic” deaths from the highly infectious disease today, saying it would not provide any further information out of respect to the families.

Clinical lead William Rainger said New Zealanders needed to be alert to whooping cough symptoms and make sure pregnant women, children and caregivers were immunised against the illness.

“While pertussis (whooping cough) notifications to public health remain very low, these fatalities indicate there is most likely undetected spread occurring within the community, and we are at risk of another outbreak,” he said.

Whooping cough, which is particularly dangerous for young babies, is spread by coughing and sneezing and infectious people can pass it on a week before their symptoms start.

If they are diagnosed early, treatment with antibiotics can reduce the infection period to between two to five days. Left untreated, they can be infectious for up to three weeks.

Whooping cough immunisations are routinely given to pregnant people at 16 weeks, and infants are immunised at 6 weeks, 3 months and 5 months. Boosters are given at 4 years and 11 years. The injections are free for under-18-year-olds, pregnant people, high-risk patients, and adults between 45 years and 65 years.

Te Whatu Ora said the Covid-19 pandemic had led to “seriously low” rates of routine childhood immunisations, “meaning children are not well protected from whooping cough and it is more likely to spread in the community”.

The latest Ministry of Health figures showed just 68.7 per cent of 6-month-olds were fully immunised.

“The opportunity is here right now to get ahead of whooping cough by catching up on routine immunisations which protect pēpē, tamariki and whānau,” Rainger said.

Whooping cough begins like a cold but the cough becomes more severe after seven to 10 days, leading to coughing fits that may end with a “whoop”, retching or vomiting.

“Parents should seek medical advice for their infant if they have a cough that ends with a ‘whoop’ sound or vomiting, and not wait for 10 days,” Rainger said.

An outbreak in 2017-19 led to 4697 cases of whooping cough in New Zealand.

There were no cases in 2020 or 2021 because of public health measures related to Covid-19, including closed borders, mask-wearing and other protective measures.

However, a small number of cases had been detected again around the country in recent months.

More than half of babies who get whooping cough are hospitalised, and around 1-2 per cent die from the illness.