Why a "universal" flu vaccine may soon be a reality

AS THE weather gets colder and the nights start to draw in, the annual ritual of the flu shot draws near. This year the world's capacity for producing seasonal flu vaccine will be somewhere in the region of 1.7 billion doses. A new shot is needed every year because there are a variety of influenza viruses that affect humans and these mutate regularly. In order to trigger immunity against the flu strains in circulation, vaccine makers must adapt their jab. Sometimes, as they did last year, they make the wrong guess about which strains will be most troublesome. Such missteps lead to shots that are far less effective than hoped. This can be a serious problem. Every year, in America alone, seasonal flu kills about 36,000 people.

Scientist have long sought something called a universal flu vaccine, which some have even described as the "holy grail" of influenza vaccination. This is a vaccine that is created once, and which protects for many years—or even a lifetime—against all manner of flu viruses. Now two groups of scientists in America say they have made an important step towards creating just such a universal vaccine.

Current vaccines trigger immunity against a protein called haemagglutinin. The head of this molecule is easy to access but mutates readily and changes from strain to strain. Both teams removed this head portion and targeted the stem of the molecule—which is harder to reach. This required some clever molecular footwork as when the molecule is beheaded, it falls apart. Both teams worked out different ways of holding this stem together in order to create a molecule that could be presented to the immune systems of animals to trigger an immune response.

In tests, vaccinated mice were fully protected against an H5 virus (a kind that is associated with bird flu), and ferrets and monkeys were partially protected. Sanjaya Senanayake, a specialist in infectious diseases at the Australian National University, says that because the work is in animals it is not clear how long immunity will last from a dose given to humans. Years more work will be needed before it is clear whether this approach will work.

But there are two big reasons to seek out a universal vaccine. One is the difficulty of matching the seasonal shot against circulating strains, given that mismatch can lead to thousands of excess deaths. The other, however, is that it a universal vaccine should significantly improve preparedness for a pandemic flu. In a pandemic flu the virus mutates so significantly that humans have little or no residual immunity to it. This can allow the virus to spread easily from person to person all around the world. The last flu pandemic, of H1N1, was in 2009. The Centres for Disease Control in Atlanta has estimated that the global death toll was more than 284,000. History is also replete with outbreaks of pandemic flu, some with far higher death tolls. (The so-called Spanish flu, a type of H1N1 which swept across the world in 1918-9, may have been responsible for between 50m and 100m people.) Many fear the next outbreak of pandemic influenza.

The good news is that even without a universal vaccine the world is better prepared than it has ever been for both seasonal and pandemic flu. Since 2006 the World Health Organisation has been working to help countries to improve their ability to protect citizens from pandemic disease. In that year it was only possible to produce 350m doses of vaccine. Since then, production capacity has been ramped up around the world, with many new manufacturers starting up in developing countries. The technology to produce vaccines in only three months is also widely available. In theory, were a new influenza pandemic to arise, manufacturers could now make 5.4 billion doses of pandemic vaccine. (The seasonal flu shot comprises three strains, while a pandemic flu would be only one strain thus allowing three times the quantity of pandemic vaccine to be produced.) With or without a universal vaccine the world is in a good position to meet the challenge of the next pandemic flu.