A new study could help reduce the number of whopping cough cases in babies.
The University of Auckland has been given a grant to research the best time for immunisations in the first crucial weeks.
Kate McPherson from the Health Research Council says babies currently receive a vaccine six weeks after birth.
"The injection is safe, even if you give it right at birth. But this is about getting the optimal time to have the best impact."
Dr McPherson says the research will look at whether a change is needed from six to eight weeks.
"You're going to be really hitting the balance in timing between when a baby is born and that first immunisation."
Since mid-2016 there has been a gradual increase in the number of whooping cough cases notified, reaching an average of 120 cases a month in adults and children across the country in 2017.