Race for a H1N1 Swine Flu VaccineMORE than two dozen pharmaceutical companies are racing against the clock to test, produce and ship more than a billion doses of swine flu vaccines to anxious populations worldwide.

But even if things proceed smoothly, delivery will not keep up with demand as the northern hemisphere enters the autumn and winter flu season, the World Health Organisation (WHO) has warned.

'We know that supplies will be extremely limited for some months to come,' WHO Chief Margaret Chan said.

Initial estimates that big pharma could crank out 94 million doses a week beginning in October have been slashed by 50 to 75 per cent due to poorer than expected yields from the so-called 'seed virus' strains developed by WHO-approved laboratories.

According to the global health authority, 25 drug companies have announced their intention to make the vaccines.

Five of those firms will account for more than 80 per cent of production: Sanofi-Pasteur in France, AstraZeneca and GlaxoSmithKline (GSK) in Britain, Baxter in the United States, and the Swiss group Novartis.
 
Significant numbers of vaccines should start to arrive within five to six weeks, they say.

Baxter , with orders for only 80 million doses has already finished several batches of its cell-based brand Celvapan, and said it will begin delivery while waiting for approval from national health authorities. GSK plans to start shipments in late September, while Novartis has said it will deliver in the fall. Sanofi-Pasteur has set targets for November and December.
 
If new strains under development at two WHO-partner labs – New York Medical College and the National Institute of Biological Standards in Britain – prove safe and more efficient, they could be slotted into the production process with only a minimal delay.