Dr Coulter said immunisation was one of the most successful and cost effective health interventions to prevent serious disease and also one of the safest.
At the end of the last reported quarter (October to December), 88 per cent of 8-month-old children in the Lakes District Health Board region had received their primary course of immunisation at 6 weeks, 3 months and 5 months on time.
The rate was up 5.2 per cent on the previous quarter, and was 3 per cent above the national target.
To be really effective 95 per cent of the childhood population needed to be immunised, Dr Coulter said.
Associate Health Minister Jo Goodhew said the current whooping cough outbreak underlined the importance of timely immunisation.
"On-time immunisation is vital to protect those most vulnerable to the disease, especially babies under the age of one."
More than 8600 cases of whooping cough have been reported since the outbreak began in August 2011 with no sign of the number of cases reducing.
Outbreaks of the disease - also known as pertussis - are also occurring in other countries including Australia, England and Wales and the United States.
The highly infectious disease is caused by bacteria which damages the breathing tubes and is spread by coughing and sneezing.
Infected babies may not be able to feed or breathe properly and can suffer serious complications such as pneumonia and brain damage.
Outbreaks usually occur at three-to-five year intervals, and last from two-to-five years.
The last two outbreaks in New Zealand were from 1999 to 2001, and 2004 to 2005.
All babies and children are eligible for free immunisations against whooping cough at 6 weeks, 3 months and 5 months of age.
Children also receive free boosters at 4 and 11 years of age.
Mrs Goodhew said babies needed to have had all three immunisations to be fully protected.
More than half of the hospitalisations for whooping cough occurred in babies aged under 1.
The current immunisation health target aims to have 85 per cent of 8-month-olds fully immunised by June 2013, 90 per cent by June 2014 and 95 per cent by December 2014.
In the last reported quarter (October to December) 89 per cent of 8-month-olds nationwide were fully immunised.
This year, 28 to 38 weeks' pregnant women have also been offered free immunisations.
Young patients offered immunisation
To improve child immunisation rates parents of children admitted to hospital who aren't immunised are being offered the chance to have their child immunised while in hospital.
This week is Immunisation Awareness Week and clinical nurse manager Bridget Wilson said all children admitted to the ward now had their immunisation status checked.
If children aren't immunised they are offered the chance to have it done before they are discharged.
Ms Wilson said immunisation was normally done on schedule with the family doctor but sometimes life could be a bit hectic and for one reason or another they hadn't had the vaccinations done.
"We are trying to make access to immunisations easier for families and taking the opportunity to bring their attention to immunisations on time and immunising on the spot.
"People are definitely happy to be given this opportunity while their child is in the children's unit," she said.
Names of children due to visit the paediatric outpatient clinic will also be checked and a note put on their files so parents can be consulted. Outpatient nurses have been trained to give the vaccination.
Whooping Cough
5 cases reported in Lakes DHB region in the first two months of 2013
94 Rotorua cases in 2012
8600 cases nationwide since outbreak began in August 2011.
Source: Institute of Environmental Science and Research