Mums who have recently given birth at Gosford Hospital might need to get their bubs vaccinated for Hepatitis B again.
Central Coast Local Health District reps have issued a big apology after shots were stored in a refrigerator too low in temperature, making them less effective.
Letters have been sent out yesterday to parents with kids born between August 1st 2017 and January 13th 2018 to make sure their little ones have received follow-up jabs to protect them.
While some will also get notices after receiving whooping cough vaccines stored in the same unit, for lacking an up-to-date immunisation record at August 1, or if mothers had Hepatitis B.
The CCLHD says children who have had their routine vaccinations at six weeks, four months and six months will not need to catch up.
The problem fridge has been thrown out and replaced, while other units have been looked over around the district.
CCLHD has also looked into whether staff's training is up to date.
If you need more info call 1800 770 100, or head to the Health District's website.