New Zealand fathers-to-be are nearly twice as likely as their pregnant partners to be undecided about immunisation before their child is born.
This matters, say researchers who now want an immunisation campaign designed specifically to target men.
The study, published today in the journal Vaccine, found that if both parents agreed on full immunisation, their infant was two to three times more likely to be immunised on time than a child of parents who disagreed.
Yet only 77 per cent of mothers and partners in the Growing Up in New Zealand study agreed on their intentions for immunising their child, with only 65 per cent agreeing to fully immunise.
The child of a father who decided during pregnancy for full immunisation was three times more likely to be immunised on time than one whose future dad had decided on partial or no immunisation - and this was independent of the mother's intentions.
"... fathers play an important role in ensuring that children get their childhood immunisations on time," said Starship children's hospital paediatrician Associate Professor Cameron Grant, one of the researchers.
"Given the importance of fathers' input into immunisation decision-making ... aiming immunisation campaigns specifically at fathers-to-be could be an effective measure to increase immunisation timeliness for New Zealand toddlers."
Maternity-care providers approached by the Herald agreed that a dads campaign could help.
Ann Hanson, general manager of the Birthcare maternity hospital in Parnell, said all women were given the Well Child book after giving birth and it contained information about child immunisations. But it tended to be mothers who took the child for the injections, she said, so it might be helpful if men were given more information so they could be more involved.
A father's view: 'We would be mad not to'
Jamie Waters was fully involved in the decision to immunise his children.
Because of his and wife Sally's experiences in their native South Africa before they shifted to New Zealand in 2010, the decision was easy, they say.
The couple, who live in Auckland's Point Chevalier, have two children: Zoe, 2, and 6-month-old Jackson.
"It has been an easy decision because in principle I understand why it is a good idea and agree with the reason behind it," said Mr Waters.
"I was quite surprised that there is so much choice for parents here. We come from South Africa where ... things like TB are more prevalent. I know exactly how bad those can be and you err on the side of caution for everything.
"I think we would be mad not to [immunise]."
Mrs Waters said: "We have, first-hand, seen what not having a vaccination can result in."
Her grandmother, now 93, contracted polio as a child - the first vaccines came into use in the 1950s - and the disease left one leg with "no muscle - it's very thin, about half the size of a normal leg".