A toddler who contracted diphtheria of the throat in northern NSW has had to be intubated in ICU, and a second child is also in hospital with the infection, public health authorities say.

The two children were close contacts, and a larger outbreak was not expected, said Dr Paul Douglas, from the North Coast Public Health Unit.

On Saturday, the two-year-old from northern NSW was admitted to ICU in a Queensland hospital, and the following day, a six-year-old was hospitalised “as a precaution” in the same area after being diagnosed with the infection.

Although only 86% of two-year-olds in the region are vaccinated — well below the state average of 92.5% — Dr Douglas said the overall coverage was likely high enough to keep the risk of transmission low.