Two unvaccinated children from the far north coast of New South Wales have contracted rare cases of diphtheria of the throat.
NSW Health confirmed on Saturday that an unvaccinated toddler was in intensive care in a Queensland hospital after contracting the infection.
Now a close family contact, aged 6, has also tested positive and is in hospital care.
NSW Health said the cases of diphtheria by the throat are the first in the state since the early 1990s.
In 2018, the Northern Rivers saw its first case of toxigenic diphtheria in 17 years.
Dr Paul Douglas from the North Coast Public Health Unit said doctors at Tweed Hospital quickly identified the first case of the potentially deadly infection.
"The child was not immunised and had the classic features of what you would see with diphtheria."
These include a greyish-green fluid on the back of their throat and tonsils, a fever, and sore throat.
The first child identified with the infection was initially treated at Tweed Hospital before being transferred to Queensland.
The children are receiving antibiotics, other close contacts are being monitored and have been provided antibiotic therapy and anti-toxins.
Dr Douglas said he was concerned about vaccine fatigue and hesitancy following the COVID vaccine roll out.
"For these really basic childhood illnesses, which are vaccine preventable, we would really encourage people to get vaccinated."
Northern Rivers paediatrician Chris Ingall said the close contact cases highlight the value of vaccination.
"Young children don't have a very good immune system," he said.
"It's a very serious disease."
Diphtheria was a common cause of death in children up until the 1940s but now occurs mainly in countries with poor immunisation levels, according to NSW Health.
The infection is spread through coughing and sneezing, and can also spread by contact with contaminated surfaces.
