The region recorded 35 influenza cases between January and September compared with an average of 114 cases for the same period over the past five years.

“The flu season has been much milder this year and influenza case numbers continue to remain low in NSW, including across WNSWLHD,” a spokesperson said.

“There are many possible explanations for the milder flu season but one important factor is the increased number of people getting their annual flu shot this year.

The WNSWLHD said about 145,000 doses of influenza vaccine were provided for the health district staff – an increase of 30 per cent on 2017.

Flu outbreaks have also come down across the state this year, with 28 outbreaks between January and September this year compared with 588 during the corresponding period last year.

There were 279 flu outbreaks in 2016, 103 in 2015, 120 in 2014 and 12 in 2013.

The flu vaccine was free under the National Immunisation Program for pregnant women, most Indigenous people, those aged 65 years or more, or for those who have medical conditions such as severe asthma, diabetes and heart problems.