MedImmune Inc. finally announced good news yesterday about its disappointing nasal flu vaccine FluMist: A new formulation works just as well when stored in a refrigerator as the old version does when it is frozen.

The Gaithersburg company had been testing a liquid, rather than frozen, form of the flu vaccine in efforts to win federal approval for a new version of the vaccine for the 2007-08 flu season.

Storing the vaccine in a freezer has been a major impediment to widespread adoption of the novel intranasal vaccine. Standard flu shots are kept in refrigerators, and many doctors' offices either don't have freezers or don't want the hassle of storing vaccines different ways.

Although MedImmune officials said they were pleased with the new study, they are eagerly awaiting results, expected later this year, on tests using the refrigerated version on children 6 months to 5 years old, a potentially lucrative market where FluMist might have an edge over painful injections.

FluMist is currently approved only for healthy patients 5 to 49.

Edward M. Connor, MedImmune's executive vice president and chief medical officer, said the goal ultimately is to prove that FluMist is superior to a flu shot. MedImmune officials have previously said that would be a major factor in deciding whether to continue selling the vaccine.

The company launched FluMist for the 2003-04 flu season with a $25 million ad campaign, charging more than double the price of a flu shot, but FluMist never caught on with consumers. The company sold fewer than 500,000 of 4 million doses.

MedImmune planned to produce only 1 million to 2 million doses for this past flu season, and it cut the wholesale price from $46 to $23.50 a dose. But in October, Chiron Corp. announced that it could ship less than half of the U.S. flu shots needed because of manufacturing problems in England.

Federal health officials scrambled to find more vaccine, advising healthy people to avoid the flu shot and encouraging them to use FluMist. The company wound up selling about 2 million doses.

Minerva Velasquez loads trays in 2004. MedImmune is developing a new FluMist formula.