This year's National Immunisation Program flu jab protects against the four strains of flu predicted to circulate in Australia over the winter months.

What is the Australian government's line on flu jabs?

The Federal Department of Health recommends that everyone from the age of six months should be vaccinated. It offers free vaccines to those who face a high risk from influenza and its complications, such as people over 65 and those with conditions including diabetes and heart and lung disease. Vaccinations are recommended from now onwards and peak flu season usually falls in July-August.

How is it made?

We have hens to thank for our flu vaccines. Selected virus strains are grown in live hen's eggs before being extracted, purified, killed, broken down into components and then mixed to create the vaccine (for this reason, those with egg allergies and vegans may want to seek advice before having the shot). It is suspended in a tiny amount of inactive sodium chloride solution. This year's government-funded jabs are bought from pharmaceutical giants, Sanofi-Pasteur and GlaxoSmithKline.

As winter approaches, so do flu vaccines. Photo: Ulrich Baumgarten

How does it work?

Influenza expert and infectious disease paediatrician from the University of Sydney, Dr Robert Booy, said the vaccination has two effects: "A couple of proteins stimulate human immune cells to make antibodies and T-cells to fight those particular strains of flu." 

Dr Jenny Smiley gives Elizabeth Moore a flu jab. The government recommends jabs for everyone over 6 months old. Photo: Sylvia Liber

Do the vaccines give us flu?

Yes and no. Technically, the vaccine is "killed" and so delivers only a small amount of inactivated virus, said Dr Barr. Our body reacts to the components of influenza virus in the mix, he said. "It's a much smaller response, some of symptoms may appear, but they are very short lived."

Why is 2016's jab being called a "super vaccine"?

Flu strains are termed "A" (H1 and H3) or "B". Last winter, a record 100,571 cases of laboratory-confirmed influenza cases were reported in Australia, 60 per cent of which were B viruses. Last year's government vaccination targeted three strains of the virus, two A strains and one B strain. This year's government flu immunisation is a quadrivalent, or four-strain, vaccine. The new vaccine includes an additional B strain known as the Brisbane strain, alongside the Phuket (B), Hong Kong (A) and California (A) strains. Strains are named for the locations in which they were first isolated. 

Australia is preparing for the flu season, which usually hits its peak in July-August.

How do we predict the flu strains for the winter ahead?

Australia, like most countries, takes a lead from the World Health Organisation, which has six collaborating centres for influenza, based in Melbourne, Atlanta, London, Tokyo, Beijing and Memphis. The group meets twice a year to make recommendations as to which viruses may strike the following winter, said Ian Barr, acting director of Melbourne's WHO collaborating centre.

WHO recommendations are then scrutinised by the Australian Influenza Vaccination Committee. Australia usually follows the recommendations, and has not veered from WHO advice since before 2000. This winter's northern hemisphere pandemic was the A, H1 strain, so it's very likely we'll have the same here, he said.

Will the vaccination target the right strain of flu?

"We don't know for sure, it's not quite crystal ball gazing," said Dr Barr. "We take the latest data we have in terms of trends and which viruses are circulating and try to predict which ones will be in circulation in 6-12 months, when these vaccinations will be needed."

New viruses come along, he said, and once the machinery of vaccine production starts rolling, it's virtually impossible to change the vaccine formulation.

"We're looking for next virus that is likely to dominate, that's the trick."

The flu jab is 50 to 60 per cent effective and is available free of charge of all at risk groups. Photo: iStockphoto

So, does the jab work?

It varies from year to year, but both Dr Barr and Dr Booy said the vaccine is usually 50 to 60 per cent effective. "I call that a good vaccination," said Dr Booy. "Excellent would be over 90 per cent effective."

2000 to 3000 Australians die from the preventable disease annually, a figure that he believes we could "do better at" reducing - in part by having the vaccine.

The overwhelming majority of research finds in the flu jab's favour, though a 2013 report in the British Medical Journal by Peter Doshi criticised the promotion of influenza vaccines in the USA as "one of the most visible and aggressive public health policies today." Closer to home, Peter Collignon, professor of microbiology at the Australian National University, has raised concerns over whether the vaccination may increase susceptibility to new strains of flu and questioned its effects on mortality rates.

How many people have the shot each year?

No-one really knows. According to the Australian Childhood Immunisation Register, almost 72,000 children under the age of seven received the influenza vaccination in 2015. In 2014, the figure was 47,000. However, not all vaccination providers routinely send this information to the Register.

There is no national register for recording immunisation amongst adults (including against influenza), though from September, the new Australian Immunisation Register is hoped to capture all vaccinations from cradle to grave.

How much does it cost?

The government has set aside $31.3 million for up to 4.48 million free doses of the new flu booster, which became available last week. High-risk groups such as those mentioned above and pregnant women and young Aboriginal and Torres Strait Islander children are not charged for the vaccination. Both types are available privately, with the quadrivalent jab costing around $25 plus the GP consultation. The trivalent jab can cost as little as $9, with many pharmacies now providing flu vaccines.

What do doctors recommend?

Most take a lead from the government and the WHO. Healthy people will receive good protection from the trivalent jab, while high-risk groups should seek the quadrivalent vaccine, said Dr Booy. He recommends jabs for all of those who work with the young or old, or in hospitals and health centres.

Are there any alternatives to having the jab in terms of prevention?

Staying fit and healthy is key. Wash your hands thoroughly and regularly, use tissues and keep surfaces clean, say public health experts.