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Why isn鈥檛 the flu vaccine better?

Nearly all flu vaccines are made of viruses grown in hens鈥� eggs, a process dating from the 1940s that takes between six and eight months. One egg is inoculated with a flu virus that grows well in eggs and has been equipped with the H and N proteins from a virus strain thought likely to circulate next winter. The world has the capacity to make 1.5 billion doses of vaccine each protecting against three or four strains, and so each requiring three to four eggs. Vaccines this year contain both the circulating A strains, and one or both of the Bs. .

This process means virologists must predict months in advance which viruses will circulate so companies can grow the right vaccines. Sometimes they get it wrong, although this year the vaccine virus was a good match, says of the University of Melbourne.

There is still a problem, though. A review last year found that the main, injected vaccine, made of killed viruses, protected 鈥� which is the dominant strain this year. This fell to 24 per cent in the over-65s. In the Australian winter just past, the vaccine protected only 10 per cent of recipients of any age from H3N2, and made no difference in elderly people, although it worked as well as usual against the other strains. The same vaccine is being used for the northern flu season.

That seems to be down to mutations during the vaccine鈥檚 production. In October, researchers at the University of Melbourne found that antibodies to the H3N2 strain used to make the vaccine worked fine against the H3N2 viruses that actually circulated, but when it was grown in eggs, the viruses that emerged .

Simultaneously, a California team showed that one mutation common in egg-grown H3N2 makes unexpectedly large changes to the injected virus鈥檚 surface protein, so .

It still makes sense to get vaccinated: in Australia this past season.

Can we make a better vaccine?

Growing annual flu vaccine in hens鈥� eggs is cheap. A few manufacturers grow vaccine virus in cultured mammalian cells, but this is 20 times more expensive, still takes between six and eight months, and .

One innovative technology is to base vaccines not on a whole virus, but on just its surface proteins. of Meriden, Connecticut, puts genes for flu鈥檚 big surface protein into insect cells and harvests the protein. The vaccine has been approved in the US, and Sanofi, the world鈥檚 biggest maker of flu vaccine, has bought the company. Medicago of Quebec City in Canada . These vaccines could be made in large quantities in weeks, not months 鈥� and shortly before flu season, making them more likely to match what circulates, without egg-based mutations.

The real game changer, though, would be a 鈥渦niversal鈥� vaccine that elicits immunity against parts of the flu virus that stay the same over time or between strains. This wouldn鈥檛 need to change every year, and could be stockpiled for pandemics. People have been trying to develop one for years, and there are promising candidates. But the world spends only $35 million on the research each year, says Mike Osterholm of the University of Minnesota, hardly enough to bring a vaccine to market. With millions sunk into making the existing vaccine, companies have little incentive to spend on new ones.

Governments are funding efforts to fix that same market failure for other potential plagues such as Ebola. But no one is doing it for flu, even though as populations age ordinary winter flu can only become a bigger killer 鈥� even if you don鈥檛 count pandemics.

This article appeared in print under the headline 鈥淲inter flu: Everything you need to know鈥�