LONDON - The H1N1 swine flu pandemic should spur pharmaceutical researchers to renew efforts to develop a universal flu vaccine and rethink ways of dealing with future pandemics, scientists said on Friday.

Flu experts from the World Health Organization, Swiss drug giant Novartis AG, the U.S. National Institutes of Health and others noted that the arrival of H1N1 had prompted a jump in the potential output of vaccine manufacturing to 900 million doses from 400 million.

But in a letter to the journal Science, they urged drug and health industries to be more proactive in developing and distributing vaccines -- and in particular to speed up the search for a universal flu vaccine.

"Although the H1N1 pandemic has the potential to cause a social and economic emergency, it also provides an opportunity to rethink our approach to influenza virus disease and to develop more effective vaccines and economically sustainable solutions for developing and developed countries," they wrote. "Research toward development of a universal vaccine should be accelerated."

A universal flu vaccine which would combat all strains of the virus has so far eluded pharmaceutical firms and scientists.

Inovio Biomedical Corp, which is working on such a vaccine, said this week that it expects initial evidence early next year on whether the technology it is using can help to fight diseases.

Johnson & Johnson, the world's biggest diversified health care company, recently bought a stake in Dutch biotech firm Crucell partly to get hold of flu-mAb, a universal antibody engineered to prevent and treat infections from various influenza A strains.

The swine flu outbreak was declared a pandemic in June and has already infected millions of people around the world. Drugmakers and governments have been scrambling to make and supply vaccines targeting the new H1N1 strain before a feared second wave of infection hits as the northern hemisphere heads into winter.

The flu experts, including Dr David Salisbury, director of immunization at Britain's Department of Health, and Dr John Treanor, who tests flu vaccines at the University of Rochester Medical Center in New York, criticized the current approach to flu as "reactive rather than anticipatory."

"We have already learned a great deal about fighting influenza, but we need to move from a reactive to a proactive and sustainable stance," they wrote.

They said better flu surveillance methods were needed in developing countries to understand how such viruses circulate globally and affect morbidity and mortality.

They also proposed strengthening epidemiological studies in developing countries to try to fill "knowledge gaps" about the virus, including the role of antibodies, immune memory, and T-cells that recognize and destroy viruses.