More than 400 babies have been infected with the flu in Victoria so far this year and the season's early start has seen huge numbers of children admitted to hospital with the virus.
With the state in the grips of a major flu season that began about three months earlier than usual, Victorian Health Department figures reveal there have been 416 reported cases of influenza in babies under 12 months old, compared to 29 cases at this time last year, an increase of more than 1300 per cent. In 2017, there were 55 cases over the same period.
Data from six major hospitals also shows there have been 338 children admitted for influenza. There had been just 15 at the same time last year.
Royal Children's Hospital paediatrician and specialist Margie Danchin said the high number of sick infants highlighted the importance of vaccination in young children and expectant mothers.
Health guidelines recommend pregnant women get a flu vaccine to protect themselves from serious complications – which Associate Professor Danchin says are twice as likely during pregnancy – and crucially to protect the baby by transferring immunity via the placenta.
Babies cannot receive a flu vaccine until they are six months old.
"In a bad year where a lot of flu is circulating in the community, young infants are the most vulnerable and if they don’t have any maternal antibodies on board, they are more likely to be admitted to hospital," Associate Professor Danchin said.
“Deaths [from flu] in children are highest in infants under six months old.”
While people over age 65 and under age five are the groups most vulnerable to influenza, Associate Professor Danchin said young babies were particularly at risk without maternal vaccination as they were unprotected until their first flu shot.
She says maternal vaccination protects 60 per cent of babies from catching the flu in their first six months of life. It also reduces the severity of the virus, with 90 per cent of infants protected from being taken to hospital.
Victoria's Chief Health Officer Dr Brett Sutton said protecting a baby with maternal vaccination was "critically important".
"It's protecting the baby before they're old enough to get the vaccine. It's more powerful than getting members of the family vaccinated," Dr Sutton said.
But uptake is not as high as hoped. Dr Sutton co-authored a Victorian study published in April in the Medical Journal of Australia which found 39 per cent of pregnant women were vaccinated against influenza.
It's worrying in a big flu season, which Dr Sutton says brings greater risk for babies.
More than 34,400 Victorians have been diagnosed with the flu this year and at least 26 have died, including three children.
Associate Professor Danchin said the number of flu presentations to the Royal Children’s Hospital had already exceeded that of the whole of 2018, and 19 children had been treated in intensive care.
“We have seen a large number of children and infants admitted to the hospital this year and the majority that are admitted are under-vaccinated," she said.
“I have been quite distressed on a personal level ... The crushing lethargy you see in a child, they’re listless, you can tell they are just aching."
She said it wasn't too late to get the vaccine as it was unknown when the flu season would begin to wane.
"It's our highest flu season on record year to date and we don't know when it will begin to reduce," she said.
Pregnant women and children aged six months to five years old are eligible for a free flu shot.
Dr Sutton urged Victorians who were yet to be vaccinated to consider the benefits for society's vulnerable, not just themselves.