In 2018, 10.84 million vaccine doses were distributed across Australia to prevent another flu season that saw more than 249,000 laboratory-confirmed cases of influenza last year.
There were 1,100 influenza-associated deaths in 2017, with over 90 per cent killing people aged 65 years and older.
The infection also affected hundreds of thousands of Australians.
But 83 per cent fewer people fell sick in 2018, according to figures up to 1 October from the .
In New South Wales, there were 86 per cent fewer laboratory-confirmed cases of the flu compared with the same period in 2017.
The trend was reflected in South Australia and Victoria - approximately 86 per cent and 88 per cent fewer cases respectively - during the same period.
Annual Australian laboratory confirmed flu numbers. Source: AAP
In Queensland, despite 10,558 laboratory-confirmed influenza cases, the year to date count was 0.2 times the count for the same period last year.
In WA there have been 1,609 fewer cases of the flu so far, only 175 cases of the flu in total in the Northern Territory and only 375 cases of the flu in the ACT.
In Tasmania, there have been only 262 counts of the flu compared to more than 3,500 cases in 2017.
Why were there fewer flu cases this year?
The lower rates have been put down to a variety of factors that have contributed to a mild season compared to the record numbers seen in 2017.
The president of the Australian Medical Association NSW Dr Kean-Seng Lin told SBS News: “The reasons why one flu season is worse than another are often very complex. It relates to issues such as how virulent or how severe the flu virus is for that year, as well as how well the influenza vaccine for that year works."
"So it is quite common to see influenza rates vary quite dramatically from year to year. And often when you have one really bad year, you have a year which is not so bad the year after."
Victoria's Deputy Chief of Health Dr Brett Sutton said while it was too early to gather the specific data, he believed this year's vaccine was considerably more effective.
"Last year we saw a lot of the particular strain called H3N2. That was particularly severe for the elderly," Dr Sutton told SBS News.
"This year we have seen a different type of influenza A, which is called H1N1."
Immunising the vulnerable
Dr Sutton said this year there was a concerted effort to reach those at risk. This included rolling out the free immunisation of children between six months and five years of age.
"Not only does it protect them [under-fives] directly, which no doubt has had an impact on numbers, but they are also part of the chain of transmission spreading to others, family members and other vulnerable groups," Dr Sutton told SBS News.
"In Victoria, it was at least 25 per cent [uptake] and for Aboriginal kids under five years of age it was 33 per cent. So we had pretty good coverage for under-fives."
A National Immunisation Program sign is seen behind Australia's Chief Medical Officer Professor Brendan Murphy during a visit to SIA Medical Centre. Source: AAP
In New South Wales, the government spent $22.75 million on state-wide immunisation programs, which included $3.5 million on free flu shots for children up to five years of age, according to a NSW Health spokesperson.
It also issued an extra 2.3 million doses since April up until September, which was 50 per cent of the total number distributed in 2017.
A degree of natural immunity may have also protected those that fell ill with the flu.
“Obviously last year was such a huge season by way of numbers, literally hundreds of thousands of people got infected with the flu and so those people went into this season with a degree of natural immunity," Dr Sutton said.
“That is one factor. They were actually protected because there were just so many people who got the flu last year that many of them weren't going to get it this year."
Flu season not over
Despite a downward trend in reported flu cases across most states and territories, SA Health's Communicable Disease Control Branch Director Dr Louise Flood said South Australia has seen a slight rise in cases last month.
“This is the time of year that we typically see the majority of flu cases, and the latest notifications show that many people are now falling ill,” Dr Flood said in a .
“There has been high demand for the flu vaccine this year and a national shortage at the beginning of the season, however that has now eased and vaccines are readily available.
“While the number of cases we have seen this year is only a fraction of last year’s record flu season, it doesn’t make flu any less dangerous and potentially deadly.”