Why didn't my flu jab work this year?

The flu vaccine's effectiveness may have dropped below 40 per cent this year, experts say, as flaws in its manufacturing and design become apparent.

The current vaccine is grown in eggs - but scientists are now concerned that may cause it to mutate, rendering it less effective.

Worse, the vaccine is only 20 to 30 per cent effective against the deadly virus strain running rampant through Australia's nursing homes. When administered to the elderly its effectiveness falls even further.

In response, experts are demanding the federal government introduce two new super-vaccines that are available overseas but not here.

"Even when the virus-vaccine match is perfect, the vaccine typically only yields about a 70 per cent effectiveness. That really is a reflection the vaccine is not perfect," said Associate Professor Aeron Hurt, part of the Australian team at the World Health Organisation working on the vaccine.

"Really, all we can do here is try to get the match as close as we can."

More than 180,000 cases of flu have been confirmed nationally this flu season, two and a half times the number of cases over the same period in 2016. In NSW three children were among 288 flu-related deaths, while in Victoria 95 people have died of flu-related conditions in 2017, according to the latest state-based data.

There is also work afoot to improve antiviral medication such as Tamiflu, which is used to treat and sometimes prevent the flu.

Melbourne-based biotech company Aus Bio is undertaking preclinical research into a drug it says will need to be taken only once every 12 days to prevent the flu (Tamiflu is taken twice a day).

University of Melbourne virologist Professor Lorena Brown said the drug compounds would change the shape of the influenza virus, so it was no longer infectious.

"The antiviral compounds that we have at the moment just make the release of the virus from infected cells inefficient, so it is a much more powerful way of combating a virus," she said

Professor Brown said the drugs could be particularly useful in flu seasons where the vaccine was ineffective against the circulating strains, as it could be used to give additional protection to those in aged care and other vulnerable people.

While she said the flu vaccine was always the best way of preventing the flu - it was not possible to accurately predict what strains to include in it.

The flu vaccine's effectiveness fluctuates each year depending on how good the "match" is between virus and vaccine, but overall it averages about 50 per cent effectiveness. Typically the risk of an individual catching the flu is between 5 and 10 per cent a year, so a 50 per cent effective vaccine cuts that rate to 2.5 to 5 per cent.

But Allen Cheng, a professor of infectious diseases epidemiology at The Alfred hospital, believes its effectiveness has fallen below 40 per cent this year.

"There are vaccines that are better, and although they aren't perfect it would be good to look at these a bit more closely and consider bringing them to Australia," he said.

Despite that, experts and the government strongly recommend getting the jab every year, particularly for people who are elderly or have other risk factors.

The flu vaccine targets four strains of the flu: H1N1, two B strains and H3N2. It is highly effective against H1N1 and B strains, but only 20 to 30 per cent effective against the H3N2 strain.

Unfortunately the H3N2 strain has been dominant this flu season. It is also the strain that affects the elderly the most. The elderly are also the most difficult to vaccinate, due to a weakened immune system.

As well as being potentially lethal itself, the flu can open the door for potentially fatal bacteria, such as golden staph.

Experts say flu season peaked in mid-August, though the number of new cases remains at high levels.

Professor Hurt from the World Health Organisation called for federal Health Minister Greg Hunt to urgently roll out the two new vaccines.

One contains four times the dose of flu vaccine; the other a chemical that boosts the immune response and therefore the vaccine's effectiveness.

"Studies for both of those two vaccines suggest they do result in much improved effectiveness, particularly in the elderly," Professor Hurt said.

Mr Hunt's spokesman said the minister had asked Chief Medical Officer Professor Brendan Murphy to work with manufacturers to investigate bringing the new vaccines to Australia.

This story Why didn't my flu jab work this year? first appeared on The Sydney Morning Herald.