"However, the first dose isn't given until six weeks, so for those first few weeks babies have no protection against pertussis."
Dr O'Connor said that could be changed by pregnant women being vaccinated.
"Pregnant women can be vaccinated between weeks 28 and 38 of their pregnancies. The reason for this is if they get a booster shot they will then produce anti-bodies which will protect their babies in the first six weeks of their lives."
Whooping cough is a highly contagious disease which starts like a cold, with tiredness and sometimes a mild fever. Coughing then develops, usually in bouts, followed by a deep gasp, or "whoop".
In adults, who often do not develop the "whoop", the painful symptoms last from two weeks to a few months and are highly contagious. And while the number of adults contracting whooping cough is on the rise - Dr O'Connor said half of Wanganui's cases during the current epidemic were aged over 20 - it's still infants that are most vulnerable. Very young children can develop long-term lung or brain damage, or even die.
Dr O'Connor said no one in Wanganui had died of whooping cough in the current epidemic, but whooping cough had killed two New Zealanders in 2012.
He said Wanganui had very high rates of immunisation, but the whooping cough vaccine did not give life-long protection.
New Zealand experienced a whooping cough epidemic every three to five years.
"The explanation for this is that with an epidemic comes increased immunity in a community, but that falls away, and the disease is able to get a foot-hold again."
Dr O'Connor said the rate of whooping cough notifications had dropped slightly over the past few months, but it was too soon to say the epidemic was on its way out.
