By Ben Hirschler and Sam Cage

LONDON/ZURICH (Reuters) - Drugmakers said on Sunday they could supply millions of doses of medicine and were ready to work on a vaccine against a new type of swine flu that has killed up to 81 people in Mexico and infected around a dozen in the United States.

Roche Holding AG's Tamiflu, known generically as oseltamivir, and GlaxoSmithKline Plc's Relenza, or zanamivir, are both recommended drugs for seasonal flu and have been shown to work against viral samples of the new disease.

Tamiflu is expected to be in greatest demand should swine flu develop into a pandemic, as experts fear it may, since it is given as a tablet. Relenza must be inhaled.

Roche said it has a stockpile of 3 million packages of Tamiflu ready for use by the World Health Organization (WHO), half held in the United States and half in Switzerland.

"So far the WHO has not requested we deploy this stockpile. Of course, as soon as the WHO requires that we deploy it we will do so," said Roche spokeswoman Claudia Schmitt.

Both Roche and Glaxo said they were in contact with the WHO, U.S. authorities and the government in Mexico.

The two companies have received contracts in recent years from individual governments and corporations for stockpiles of their medicines, following earlier fears over bird flu.

Those sales provided windfall profits, especially for Roche, and also benefited their respective partners. Tamiflu was originally invented by U.S. biotech company Gilead Sciences Inc, while Relenza was licensed to Glaxo by Australia's Biota Holdings Ltd.

The longer-term battle against any pandemic, however, depends not on antiviral drugs but a successful vaccine.

Making a vaccine against a new strain of flu takes months and vaccine companies said they were on standby to start the development process as soon as possible.

Leading flu vaccine manufacturers include Sanofi Pasteur, the vaccines division of Sanofi-Aventis SA, Glaxo, Novartis AG and Baxter International Inc.

"Sanofi Pasteur, as the world leading producer of influenza vaccine, is standing ready to assess its capabilities to support public health efforts, should the WHO and other health authorities request support from influenza vaccine manufacturers," said spokesman Pascal Barollier.

As yet, though, the WHO has not taken the step of distributing virus samples to companies for them to develop a new vaccine.

(Editing by Elaine Hardcastle)

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