Anthony Hurst is among the thousands of parents now waiting an agonising month before they can be sure their children have escaped the contamination scare.
The North Shore father's 8-month-old twins, Amelia and Joshua, were fed from the recalled batches of Karicare formula until Monday morning.
"We are two very concerned parents who have found absolutely no reassurance from Fonterra in its communications about any of its baby formula products and will never be able to return to this brand with a clear conscience when we feed our children."
After years of trying, Amelia and Joshua were finally born. The babies spent a period in the neonatal intensive care unit and were fed Karicare by staff.
Mr Hurst said he and his wife, Maria, were "loathe to change" brands out of fear of giving the twins something they didn't take to.
They bought the infant formula in bulk and unfortunately it was some of the recalled batch - they've been using it for the last few weeks.
If information had been clearer and more quickly delivered by Nutricia and Fonterra, Mr Hurst said they would have stopped as soon as they knew there was an issue.
"We are now on S26 and I have to say I cannot see us ever going back to Karicare such has been their mishandling of the information they have put out since this story exploded.
"I sincerely hope that the final story here is not about infants falling ill, but about how badly a company which is the largest in the country and a global brand has shown itself to be an absolute failure when it comes to communication with its markets both locally and internationally."
Mr Hurst said they have to wait 30 days before they know if their children are in the clear.
Botulism symptoms can take anywhere between three and 30 days to develop, and the couple can't help but worry. Every bit of drool makes them wonder whether it's "normal drool or whether it's [a symptom]".
"This is a fail from a huge company that should be able to do so much better at simple communication of information that they should have on hand and be confident of.
"Their inability to tell us with confidence that our two babies will not fall ill from any of its products now nor from the contaminated products in the next 30 days is unforgivable."
Yesterday, parents were still flooding helplines. The Karicare call centre has had more than 6000 calls since the news broke on Saturday.