In two developments that could help avoid a recurrence of last year's influenza vaccine shortage, the government yesterday said it approved a new flu shot and took a step toward allowing a major flu-vaccine supplier to resume distribution in the country.

Only two manufacturers sold flu vaccines in the United States last year, down from up to five within the past 20 years, a fact drugmakers blame on the high cost of producing the doses and the fluctuations in demand every year.

But the Food and Drug Administration's approval of Fluarix, produced by GlaxoSmithKline PLC for adults 18 and older, will introduce a third supplier for the coming flu season, which typically begins in October. The British company is expected to produce 8 million doses for the United States this year.

That will add to what is already in the pipeline: Sanofi Pasteur is expected to ship up to 60 million doses to the United States, and MedImmune Inc. of Gaithersburg is slated to make about 3 million doses of its nasal-spray flu vaccine, according to the U.S. Centers for Disease Control and Prevention.

Overall, the CDC predicts that companies could manufacture 80 million to 100 million doses of flu vaccine for the United States this year, up from 61 million in 2004, when communities across the country rationed out the vaccine.

In a statement, Health and Human Services Secretary Mike Leavitt called the approval of Fluarix "a big step toward providing an adequate supply of flu vaccine for the American public."

The vaccine supply could receive another boost if the FDA clears Chiron Corp. to distribute its flu shots in the United States. In 2004, British authorities impounded 48 million doses of flu vaccine intended for the United States because of bacterial contamination at the company's manufacturing plant outside Liverpool, pinching the overall U.S. supply.

The FDA yesterday said Emeryville, Calif.-based Chiron had passed an inspection at its British factory, helping clear the way for FDA approval to sell flu shots in the United States. But the agency cautioned that "additional work is needed to determine the amount of vaccine Chiron may be able to supply the U.S. market for the upcoming flu season."