A record number of flu cases this year has prompted the government to plan a roll-out of a stronger vaccine for Australia's most vulnerable next year.

Australians most vulnerable to the flu will get free access to stronger vaccines in 2016 following a record number of cases this year.

The government's national immunisation program will now include a vaccine that covers four flu strains instead of three, including two influenza B strains that wreaked havoc in the 2015 flu season.

Flu cases soared from 65,000 in 2014 to almost 93,000 this year, with influenza B strains responsible for an estimated 62 per cent.

A government decision to delay this year's flu immunisation program until sufficient supplies were available may have contributed to the record level of cases.

The program was delayed by a month as manufacturers scrambled to update two of the three influenza strains in their vaccines in response to a bad flu season in the northern hemisphere.

Health Minister Sussan Ley said on Friday the higher number of cases could be because more people were taking their flu symptoms seriously and visiting a doctor.

She said the new vaccine was consistent with World Health Organisation recommendations and meant "the best possible protection will be available free to the people who most need it".

It will cover the influenza A California and Hong Kong strains as well as the Brisbane and Phuket influenza B strains.

There will also be a vaccine specifically for children under three.

The vaccine will be available for free to pregnant women, people over 65, indigenous Australians in certain age brackets and those with specific medical conditions.

Those not eligible for the government program can get the vaccine from their GP or employer.