Drug-buying agency Pharmac says New Zealand's supply of the oral medicine used to treat children with RSV is critically low.
Usually the consumption of Prednisolone, a steroid medication, has been around 8500 bottles for 12 months. But during June the number of bottles ordered by community and hospital pharmacies almost doubled to 15,250.
Pharmac said the supply was now critically low, raising concerns pharmacies would not be able to access the drug.
The agency said it was working to get supply back into the country quickly, but expected stock would run out quickly.
It said it was working with the supplier and airfreight to get the next order in before the end of the month.