One of the problems with use of vaccines to stop a flu pandemic is that it takes many months to develop and manufacture vaccines against a new flu strain. Even worse, the manufacturing capacity for making vaccines is woefully inadequate for the case of a global pandemic. In a pandemic the need for vaccine would go up over an order of magnitude and the current process for making flu vaccine is hard to scale up. One way to partially solve this problem would be to manufacture vaccines in advance using flu strains that are not exact matches for an eventual pandemic strain. Support for pre-pandemic vaccine production is building.

"People are taking pre-pandemic vaccination seriously," says Derek Smith at the University of Cambridge. In May, a meeting of scientists and manufacturers at the World Health Organization in Geneva, Switzerland, recommended the development of vaccines that could be used to inoculate people before a pandemic takes hold. These, they said, must have long-lasting effects, and be "broad-spectrum" enough to work against whatever pandemic virus emerges. Several novel vaccines that do both are now close to testing in humans. They include the addition of immunity-stimulating chemicals called adjuvants, vaccines made of DNA instead of the virus itself, and perhaps the ultimate - a vaccine that protects against every kind of flu.

While there is no way of knowing before a pandemic starts exactly how well the vaccine will work, the risks of doing nothing could be far greater. "Stockpiling pre-pandemic vaccines is more valuable than people realise," Robert Webster of St Jude Children's Research Hospital in Memphis, Tennessee, told a flu conference in Singapore last month. "It may not necessarily protect you from infection, but it will probably stop you dying."

I've been in favor of this idea for years and continue to think that movement in the direction of developing pre-pandemic vaccines is too slow. The problem with pre-pandemic vaccines is that they won't be an exact match for whatever strain of influenza eventually becomes pandemic. But if an H5N1 avian flu strain mutates into a human pandemic strain then even a vaccine made from a different H5N1 strain will provide partial immunity to the pandemic strain. That partial immunity might some day save millions of lives.

The article reports on promising advances in DNA-based vaccines and in adjuvants (which amplify immune system response to vaccines). Production of DNA vaccines could be scaled up much more rapidly than the current chicken egg-based vaccine manufacturing process.