Victorian GPs and pharmacies will have enough vaccines to meet surging demand as a free jab program begins to combat a "nasty" influenza season, health authorities say.

From Wednesday to June 30, Victorians aged six months and over can get a free flu shot at one of more than 3000 GPs and community pharmacies under the $33 million program.

"This is our first real flu season for two years," Health Minister Martin Foley said on Tuesday.

"What this free program will do is protect Victorians and their families in the face of what is going to be a challenging winter."

Reported flu cases in Victoria jumped from 10,000 to 15,000 last week - more than the combined total of the past two seasons when infections were curbed by the closure of international borders.

So far this year 148 Victorians have been hospitalised with the flu, including 65 children, placing further pressure on the state's health system.

"What we do know is that after two years of no seasons, lowered immunity, that this is a nasty flu season," he said.

While some chemists may offer walk-in flu vaccine services, bookings are recommended by Victoria's Pharmacy Guild of Australia president Anthony Tassone.

"We do understand that members of the public may feel tired and fed up with vaccines ... but sadly the virus doesn't care," he said.

More than one million Victorians already eligible for a free vaccine - including children under five, people over 65 years, pregnant women, Aboriginals and Torres Strait Islanders, and those with serious medical conditions - have taken up the offer.

The new program expands that pool to six million and Mr Foley is confident "more than enough" stock is available nationally to meet demand.

The Therapeutic Goods Administration reported 16.8 million flu doses have been released into the system, with 9.2 million set aside for the National Immunisation Program, Mr Tassone said.

Dr Shea Wilcox, co-owner of Brunswick's Inner North Medical Clinic, said the initiative was fantastic but lamented the lack of forewarning and potential supply issues.

"We'll struggle to meet the demand. There are lots of staff sick and stock for flu shots has to be ordered in advance," he told AAP.

His clinic has roughly 500 flu shots in stock, which would normally be enough for four days but could be exhausted in a single day.

"We are now booked out through to the end of the week, whereas yesterday we were not," he said.

GPs and community pharmacies will be reimbursed for the vaccines and offered an extra $2000 to roster more staff and extend opening hours.

Dr Wilcox said it wouldn't be enough to cover their extra overheads.

Queensland, Western Australia, South Australia and Tasmania have announced similar free flu vaccination schemes to Victoria.

PSA national president Chris Freeman described the state-based, time-limited programs as a "band-aid for the bigger problem of funding arrangements which have not kept pace with population health needs".