Evidence emerged Thursday to show that a vaccine against pandemic swine flu may need only a single dose, giving rise to hopes that more of the H1N1 vaccine can be spread across a larger portion of the world's population.

Swiss drug maker Novartis AG (NVS) said a study shows patients may need only one dose of swine flu vaccine Celtura to be protected from the virus. Meanwhile, China approved a home-grown one-dose vaccine against swine flu produced by Sinovac Biotech Ltd. (DVA), as the country braces for a feared winter outbreak.

Basel-based Novartis said Celtura elicited a strong and potentially shielding immune response in 80 of 100 patients tested after one dose, and more than 90% after two doses were applied. The vaccine was tolerated well by the test patients, with local pain where the injection was administered the most common health drawback.

China's approval of Sinovac's single-dose vaccine and Novartis' good results with one dose could boost the global fight against Type H1N1 influenza, since most experts had assumed two doses a person would be needed to provide enough protection against the virus.

Novartis is among a host of drug manufacturers racing to produce a vaccine for H1N1, a flu virus which began sickening people around the world this spring. U.K. drug makers GlaxoSmithKline (GSK) and AstraZeneca PLC's (AZN) MedImmune are among the companies also trying to produce a vaccine for so-called swine flu.

The World Health Organization, or WHO, says at least 2,185 people have died worldwide after contracting swine flu, now the most prevalent strain of influenza. It has been detected in nearly every country in the world.

The U.N. health body has warned of a possible Type A/H1N1 vaccine shortage as winter - and the regular flu season - approaches in the northern hemisphere.

The high rate of effectiveness after one injection of Celtura is good news, given that production of the swine flu virus is expected to be lower than rates for normal seasonal flu vaccine.

"The lower production volumes of the vaccine may be spread over more patients and result in a broader coverage of the population," Bank Vontobel analyst Andrew Weiss said. He rates Novartis at buy with a CHF58 target. The initial results are expected to assist health authorities in ascertaining timings and doses of vaccine campaigns for autumn.

The U.S. Centers for Disease Control and Prevention expects roughly 45 million doses of swine flu vaccines to be available in the U.S. around October 15, with 20 million coming off production lines each week following through December.

Many drugmakers have just finished their production for seasonal flu vaccine - still seen as a serious health threat even as swine flu spreads - before shifting resources to the H1N1 vaccine.

Novartis is benefiting from the fact that it can produce batches of the H1N1 vaccine through a cell-based method, as opposed to a production system based on eggs. The cell-based method shortens the turnaround time to production to roughly three or four months, from six months for egg-based methods, Helvea analyst Karl-Heinz Koch said. He rates the stock at buy with a CHF56 target.

Novartis said a larger study of more than 6,000 adults and children is underway, but didn't elaborate on the timeline.

-By Katharina Bart, Dow Jones Newswires; +41 43 443 8043; katharina.bart@dowjones.com