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 today.

Sanofi-Aventis, through its Sanofi Pasteur division based in Swiftwater, Pa., is one of the world's biggest vaccine makers.

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 P.L.C. of Britain - which has operations in Philadelphia - also has said it will do that, and has offered to donate 50 million doses of vaccine against swine flu to 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 bad 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 has two vaccine manufacturing plants at Swiftwater, in the Poconos, 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 today 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, so far has turned down requests to donate pandemic flu vaccine, instead saying it would consider selling at discounted prices to developing countries.