TORONTO, June 23 (Reuters) - Canadian biotechnology firm Microbix Biosystems Inc <MBX.TO> plans to build and operate a new influenza vaccine plant in China, which will be one of the largest facilities in the world, the company said on Monday.

The tiny Toronto-based company said its joint venture with the Hunan provincial government should be operational in 2013 and will be able to produce 100 million doses of flu vaccine a year, a huge boost to the world's current capacity of fewer than 500 million doses.

Shares in the Toronto-based small biotech company soared 11.3 percent on the news, rising 9 Canadian cents to 89 Canadian cents by the afternoon on the Toronto Stock Exchange.

The C$200 million plant will be built in China's central Hunan. The provincial government has committed C$100 million to the project and has committed to an initial 100 million doses. The remainder of the funding will be raised by Microbix through licensing partners.

Microbix said it planned to seek regulatory approval in several countries, including the United States, Canada and Europe.

Microbix director Mark Cochran said China currently vaccinates about 2 percent of its target population against the flu, but wants to increase that to about 20 percent, or 400 million doses a year.

"It's really important for China to have a vaccinated population," he said on the sidelines of a news conference.

"It's important for us in this part of the hemisphere as well, because pandemics are grown out of interaction between humans and animals, and the more vaccinated a population you have, the better it looks from a pandemic perspective."

Health experts say a vaccine will be the best way to cope with the almost-inevitable pandemic, which would kill many more people than the seasonal flu does.

Cochran said the new factory would focus on meeting China's seasonal vaccination needs, but the company will also consider exporting the vaccine depending on the level of demand in China and around the world.

The facility will use Microbix's Virusmax technology, which will allow the plant to produce more vaccine over shorter periods of time, the company said. ($1=$1.02 Canadian) (Reporting by Leah Schnurr; editing by Janet Guttsman)

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