* Experts in daily talks on risks posed by new China virus
* Researchers analysing samples to find vaccine candidate
* Decision to make vaccine depends on whether H7N9 spreads
By Ben Hirschler and Kate Kelland
LONDON, April 4 (Reuters) - Experts from around the world are in daily talks about the threat posed by a deadly new strain of bird flu in China, including discussions on if and when to start making a vaccine.
Any decision to mass-produce vaccines against H7N9 flu will not be taken lightly, since it will mean sacrificing production of seasonal shots. And scientists warn it will take months to get any finished bird flu vaccine to the market.
But the groundwork is being laid.
The virus has been shared with World Health Organization (WHO) collaborating centres in Atlanta, Beijing, London, Melbourne and Tokyo, and these groups are analysing samples to identify the best candidate to be used for the manufacture of vaccine - if it becomes necessary.
It is still a big "if", even assuming the continued spread of the new disease, which has killed five of the 14 people that it has infected in China.
"It is an incredibly difficult decision because once you make it you have to change from making seasonal flu vaccines and go to making a vaccine for this virus," said Jeremy Farrar, a leading expert on infectious diseases and director of Oxford University's research unit in Vietnam.
That could mean shortages of vaccine against the normal seasonal flu which, while not serious for most people, still costs thousands of lives.
Sanofi Pasteur, the world's largest flu vaccine manufacturer, said it was in continuous contact with the WHO through the International Federation of Pharmaceutical Manufacturers and Associations (IFPMA), but it was too soon to know the significance of the Chinese cases.
Other leading flu vaccine makers include GlaxoSmithKline and Novartis.
Preliminary test results suggest the new flu strain responds to treatment with Roche's drug Tamiflu and GSK's Relenza, according to the WHO.
MONEY DOWN THE DRAIN?
There is no evidence yet of person-to-person transmission of H7N9 flu, and scientists do not yet know how what the strain's potential is to develop into a human pandemic. Wendy Barclay, a flu virologist at Imperial College London, said one major argument against moving too soon would be financial.
"There is a possibility now that flu researchers will all rush to work on H7N9 and grants will be awarded for intensive research to develop vaccines ... and that could be pouring money down a drain because it could be that the barriers for this virus are high enough that we don't need to worry about it."
She said scientists should first be focused on getting "the practical biology and the sequence analysis" before they decide to move on.
Since the H1N1 swine flu pandemic of 2009, in which drugmakers took six months to develop and distribute effective vaccines, manufacturers have been stepping up efforts to produce shots faster to deal with the rapid spread of disease.
It remains a lengthy process, however.
"There is presently no technology that can quickly and cost-effectively mass-manufacture vaccine," said Anton Middelberg, a flu vaccine researcher at the University of Queensland.
"Although the WHO is sending materials for vaccine development to China, it is unlikely that vaccine will be produced quickly enough to impact this outbreak."
Still, the flu vaccine community is not starting completely from scratch.
A degree of preparedness already exists because the last WHO vaccine strain selection meeting in February had already decided to consider the broad H7 virus category as a pandemic candidate.
The European Centre for Disease Prevention and Control said vaccine candidate strains had also been developed as a response to previous H7 human cases in Europe and North America.
"These candidate strains may not efficiently cross protect against the novel A(H7N9) strain, but the fact that they are moving towards development does indicate a degree of preparedness globally," the ECDC said.