Health authorities are urging more young people to get the flu vaccine amid warnings that children are at heightened risk from influenza strains circulating this season.
An 11-year-old Queensland girl was the second young person reported to die from influenza this week, after a student on the New South Wales Central Coast died days after contracting the virus.
The Doherty Institute’s Prof Ian Barr, who is deputy director of the World Health Organization’s collaborating centre for reference and research on influenza, said flu strains circulating this winter had a greater impact on young people.
“The viruses which are circulating this year are influenza A(H1N1) and B viruses – both of these viruses affect children more than the elderly,” he said. “We haven’t seen the B viruses around much for the last two years.”
Children make up a significant proportion of the 153,941 laboratory-confirmed flu cases this year to date. As of 13 July there have been 19,241 cases reported in under-fives, 31,172 cases in five- to nine-year-olds, and 18,678 in 10- to 14-year-olds.
More than a third of all cases reported nationally have been in NSW (53,343), with Queensland reporting the second-highest number of infections (48,342).
State health authorities across the country told Guardian Australia they had seen high infection and hospitalisation rates in children.
In NSW, children aged zero to 16 represented almost 47% of all admissions from emergency departments for influenza-like illness in the week ending 9 July.
Queensland’s chief health officer, Dr John Gerrard, said he was “very concerned about the increase in influenza B cases and the high rate of unvaccinated patients, particularly with school resuming this week”.
He said in a statement: “Influenza B is causing severe illness in otherwise healthy Queenslanders, young people in particular.”
“Since 1 July, 78 children aged six months to four years old were hospitalised with flu – 50 with the B strain. Only one of these children was vaccinated.”
Dr Paul Armstrong, Western Australia’s acting chief health officer, said almost 40% of those who required hospitalisation for influenza treatment in the state this year were aged under nine.
“WA data suggests that we are on track for a large influenza season, similar to 2019, which was the largest on record in WA,” he said in a statement.
A South Australia health spokesperson said: “Those aged six months to five years, and five to 15 years are experiencing more influenza infections this year than any other age group.” They noted there had been no reported deaths in children in the state. Influenza B strains accounted for about 20% of the virus circulating in SA.
Children normally overrepresented in infection rates
Dr Daryl Cheng, an immunisation consultant at the Murdoch Children’s Research Institute’s SAEFVIC, said the highest rates of positive flu cases were usually in children under five.
“They are an at-risk group,” he said, adding that testing in this age group may be higher than in adults.
Barr agreed that children were typically over-represented in flu infection rates, likely due to more diligent monitoring of symptoms and testing than in adults.
Cheng said hospitalisation rates this year were similar to pre-Covid flu seasons. Historical figures show that hospitalisation rates in children under five are much higher than in elderly people.
Data recorded between 2006 and 2013 found that hospitalisation rates were highest in children aged zero to five months (192 per 100,000), followed by those aged six to 23 months (109 per 100,000).
Flu deaths in kids rare
Influenza is a leading cause of vaccine-preventable death in Australian children, but flu deaths in young people are rare.
Cheng has noted “no anomaly or spike” in child deaths from influenza this year to date in Victoria. “That doesn’t mean people shouldn’t get the vaccine [to] protect themselves,” he said. “It’s still early in the season.”
Cheng added there had been deaths in NSW and Queensland “in age groups such as adolescents which are not eligible for flu vaccination as part of the national immunisation program”.
Between 2006 and 2013, the influenza mortality rate was the lowest in five- to 11-year-olds of any age group, at 0.05 deaths per 100,000 people, and was less than 0.35 deaths per 100,000 in under-fives.
In comparison with kids under five, those aged 65 to 74 were more than twice as likely to die from the flu; in those over 75, the mortality rate was more than 10 times greater.
In another study of Australian children hospitalised with influenza between 2010 and 2019, the mortality rate was 0.4% or one in every 2,500 children hospitalised.
FluCAN surveillance data as of 25 June, which monitors influenza admissions at 15 hospitals nationally, shows that of those younger than 16 years hospitalised with influenza this year, 5.9% were admitted to ICU. In comparison, 12.1% of adults aged 16 to 64 and 1.8% of adults aged 65 years or older went to ICU.
Vaccine coverage low
National immunisation data shows that flu vaccine coverage is low in young people, and down about 10 percentage points from last year. Only 23.6% of under-fives and 13.7% of five- to 15-year-olds have been vaccinated this year to date, compared to 61.5% of those over 65.
“I suspect it’s probably [a] combination of vaccine fatigue and reduced access to in-person consultations with GPs,” Barr said.
“Kiddies are going back to school now so there will probably be a little bit of a spike,” he added. “People should still consider getting vaccinated if they haven’t already been infected.”
Influenza vaccinations are free for children aged six months to five years under the National Immunisation Program. They are also included on the childhood vaccination schedule.
