If bird flu erupts into a pandemic, the world will need a lot of vaccine in a hurry. That would be virtually impossible with the current flu-vaccine manufacturing method, which is little changed since the 1940s.
Several companies have bird flu vaccines in development, though none is yet commercially available. Chiron Corp. of Emeryville, Calif., and Paris-based Sanofi-Aventis have begun clinical trials with vaccines that could be ready next year.
But flu vaccines traditionally are grown in millions of fertilized chicken eggs, a process that takes at least six months. The lengthy production cycle makes it hard for drug makers to keep up with mutating flu strains and limits the amount of vaccine they can produce quickly.
The egg-based method is particularly problematic for bird-flu vaccines because the disease threatens chickens, which provide the essential raw material.
So pharmaceutical companies are developing two methods -- using cell cultures and DNA cloning -- that could speed things up. But each faces hurdles in gaining official approval.
The best-known alternative is to grow vaccines in cell cultures, a decades-old technology already used for vaccines against chicken pox, hepatitis A and polio. Partly by removing the step of procuring huge stores of specially prepared eggs, it makes on-demand manufacturing possible.
Culturing flu vaccine strains using human, monkey or canine cells within sealed vats "can cut the production cycle to about four months, perhaps a little better," while vastly increasing yield, said Lei Zhong, an analyst with Banc of America Securities who holds a doctoral degree in immunology.
Annual flu vaccine preparations begin in February and shots are ready in October. Cell culture vaccines could be available by July, and if a new flu strain suddenly emerged, an updated vaccine could be produced before the flu season peaked.
Chiron, Sanofi-Aventis and other companies have produced experimental cell-culture flu vaccines, and a European product may hit the market as early as next year, Zhong said.
But analysts said a U.S. product was still at least three years away because of more-demanding regulations.
Other vaccine makers and experts are putting faith in a second alternative to egg-based vaccines, one that involves a radical shift into genetic engineering.
