French drugmaker Sanofi-Aventis plans to donate millions of doses of swine flu vaccine to the World Health Organization for use in poor countries, Chief Executive Christopher Viehbacher said Wednesday.

Viehbacher said his company is making a "flexible donation" of a total of 100 million doses of vaccines against swine flu and bird flu.

The company had committed last June to donating 60 million doses of pandemic vaccine to protect people against the bird flu virus, a type designated as H5N1 influenza.

Speaking at the Pacific Health Summit, a meeting of global officials in science, industry, medicine, policy and public health in Seattle, Viehbacher said he wants to support the request of World Health Organization Director-General Margaret Chan for common action in fighting the swine flu pandemic.

"Exceptional times require exceptional responses. We need to act responsibly, and we all have to play our part," he said in a statement.

Viehbacher said that once his company starts production of vaccine against swine flu, or H1N1 flu, it will reserve 10 percent of its output for the WHO to help fight the flu pandemic in developing countries.

Sanofi also plans to sell additional quantities of pandemic flu vaccines at a discounted price to developing countries, as production capacity allows. Rival drugmaker GlaxoSmithKline PLC of Britain also has said it will do that, and has offered to donate 50 million doses of vaccine against swine flu to the WHO for distribution in developing countries.

The bird flu virus has not spread much among humans, but last year appeared capable of creating a pandemic, leading pharmaceutical companies to make vaccine against it. Millions of doses of bird flu vaccine have been stockpiled by Western governments.

Viehbacher said the two viruses now are circulating in many countries, including some of the world's poorest regions.

"This flexible donation aims to help the WHO address the needs of these most vulnerable populations," he said.

Sanofi-Aventis, through its Sanofi Pasteur division based in Swiftwater, Pa., is the world's biggest vaccine maker. The company has two vaccine manufacturing plants there and one in Val de Reuil, France, all of which can switch from seasonal flu vaccine production to pandemic flu vaccine production.

The three plants have a total annual vaccine production capacity of about 270 million doses. Sanofi-Aventis spokeswoman Marisol Peron said Wednesday that the swine flu vaccine donation will be made over multiple years.

She said the company has already donated H5N1 flu vaccine to the WHO, but could not immediately provide the number of doses.

"We're not producing additional H5N1" vaccine, she added.

Last Thursday, after the World Health Organization declared a global swine flu epidemic, GlaxoSmithKline said it would be ready within weeks to begin large-scale vaccine production.

None of the vaccines are expected to be available before this fall.

The other major vaccine supplier to the U.S. market, Novartis AG of Switzerland, has turned down requests to donate pandemic flu vaccine.

Novartis spokesman Eric Althoff said Wednesday that the company's chief executive, Daniel Vasella, believes that finding a sustainable way to provide developing countries with access to vaccines is a better solution than one-time donations. Novartis instead is looking at selling vaccines to those countries at discounted prices, Althoff said.