The number of whooping cough cases this year has surpassed 1000, and the health agency is urging people to get vaccinated against the disease.

Officials declared a national whooping cough epidemic last Friday after weeks of consistently high case numbers, hospitalisations and unlinked outbreaks.

The latest figures from ESR show 77 cases were reported last week, which includes four hospitalised cases - three of which were under the age of 1.

That was down slightly on the two weeks prior - but immunisation leader Nikki Turner said the epidemic would be long and slow, lasting up to 18 months.

Last week's cases brought the total number of cases this year to 1009, Health NZ/Te Whatu Ora public health medicine specialist Dr Matt Reid said.

A total of 63 people infected were under 12 months old, and almost three quarters of those were hospitalised, he said.

"It's incredibly important that we do all we can to get our hapū māmā immunised," Reid said.

"Newborn babies aged under six weeks are particularly vulnerable, with Māori and Pacific babies at high risk from whooping cough.

"By getting immunised when you're pregnant, you will protect your pēpi until they can have their first immunisations when they are six weeks old."

Whooping cough: What you need to know

• Childhood vaccinations to protect against whooping cough are needed at ages six weeks, three months and five months, and again at four years
• A further booster is given at age 11 years (school year 7)
• Vaccination is free for pregnant people
• Adults are eligible for one free booster from age 45 (if they have not had four previous tetanus doses) and can get one free from age 65
• Whooping cough causes breathing difficulties and severe coughing fits. The cough can go on for weeks or months which is why it is sometimes called the "100-day cough"
• People are most infectious in the early stages - with the first signs of whooping cough usually appearing around one week after infection

Symptoms (after about one week):

• A blocked or runny nose 
• Sneezing 
• A mild fever 
• Uncontrollable coughing fits that last for a few minutes 
• Coughing that leads to vomiting 
• A thick mucus that can make you vomit or choke
• During coughing spells, young babies may gasp for air and may briefly stop breathing and turn blue

-RNZ