Tamiflu continues to work against most swine flu infections, but the virus is showing signs of resistance. (Ed Wray/Associated Press)

Poverty will prevent some countries from accessing swine flu vaccines, the head of the World Health Organization said Tuesday.

"Manufacturing capacity for influenza vaccines is finite and woefully inadequate for a world of 6.8 billion people, nearly all of whom are susceptible to infection by this entirely new and highly contagious virus," WHO director-general Margaret Chan told delegates attending a World Intellectual Property Organization conference in Geneva.

"The lion's share of these limited supplies will go to wealthy countries. Again we see the advantage of affluence. Again we see access denied by an inability to pay."

Access to life-saving interventions such as antivirals is "biased in favour of affluence," Chan said in her speech on strengthening co-operation on intellectual property and public health.

The discovery of H1N1 infections that resist the antiviral Tamiflu and the global scramble for pandemic vaccine shows the importance of innovation in keeping pace with the emergence of new diseases, Chan said.

On Monday, a senior WHO official said health-care workers in all countries should be immunized to maintain health systems during the pandemic. Pregnant women and children are also considered priority groups for access to H1N1 vaccines.

Ideally, H1N1 vaccines would also offer protection against seasonal and potential pandemic viruses, Chan said.

"This innovation has not come about yet," she said. "This would be the best and most rational insurance policy for increasing supplies and encouraging more equitable access."

Chan noted talks at the WHO's annual assembly in May on how rich and poor countries should share samples of H1N1 and other flu viruses was "one of the most difficult, and divisive, issues ever negotiated by WHO."

Current intellectual property agreements do not need to be taken apart to make them more equitable, but "international agreements that govern the global trading system can indeed be shaped in ways that favour health needs of the poor."