In early results from human tests on one of its swine flu vaccine candidates, Novartis AG said one shot of its vaccine provided enough protection against the virus, as set out by criteria by U.S. and European drug regulators.
Most experts had thought two doses of vaccine would be necessary, since swine flu is a new virus to which virtually no one has immunity. On Thursday, China approved a swine flu vaccine which its producer, Sinovac, says also works with just one dose.
"The pilot results are encouraging," said Andrin Oswald, CEO of Novartis Vaccines and Diagnostics in a statement. "This is important information for public health authorities who prepare for vaccination in the coming months with limited vaccine supply."
The World Health Organization would not comment specifically on Novartis' vaccine since it had not yet seen the data. The agency said a number of companies were working on one-dose formulations which could theoretically increase the world's swine flu vaccine supplies.
Novartis said the results were based on a British trial of 100 people aged between 18 and 50, who received either one or two shots of its swine flu vaccine. It is also testing other swine flu vaccine formulations in more than 6,000 people worldwide.
According to Novartis, people who got two injections of vaccine had a better immune response, but just one injection also provided adequate protection, within two weeks of the vaccine being given.
It is still unclear, however, what this would mean for the global swine flu supply. Not every drugmaker could simply copy Novartis' vaccine recipe. Novartis' vaccine was made using cell culture, while about 90 percent of the world's flu vaccines are made using chicken eggs.
Their vaccine also included adjuvants, a chemical component used to stretch a vaccine's active ingredient and essentially make it more efficient. While adjuvants are commonly used in European flu vaccines, there are no licensed flu vaccines in the U.S. or Canada with the ingredients.
There is also limited data on how safe flu vaccines with adjuvants are in pregnant women and children, two of the groups thought most vulnerable in a pandemic, or global epidemic.
The vaccine approved by China did not use an adjuvant, like most of the vaccines being tested in the U.S.
A handful of other major pharmaceuticals, including Sanofi-Aventis SA, GlaxoSmithKline PLC and Baxter International are also conducting trials of their own swine flu vaccines, but have not yet announced results.
Since WHO declared swine flu to be a pandemic in June, pharmaceuticals have been racing to produce a swine flu vaccine. Last month, the agency said that while production was on track, the viruses being used to make the vaccine were growing slowly, which would limit global supplies.
Swine flu is expected to surge with the return of the fall and winter flu season, and many countries have planned mass vaccination campaigns beginning in October.
As of August 23, WHO said there were more than 210,000 cases of swine flu and at least 2,185 deaths worldwide, though those numbers are a widely considered a gross underestimate because hard-hit countries have stopped counting individual cases.