MedImmune ( MEDI) says it remains on track to have an improved version of its nasal spray vaccine FluMist ready for the 2007-08 flu season, even though federal regulators have asked for more information about the product.

The Food and Drug Administration is seeking "clarification and additional information related to data previously submitted," the company said Tuesday. MedImmune expects to respond within two to four weeks.

"We are confident that our continued interaction with the FDA will result in approval of the new formulation of our intranasal vaccine in advance of the 2007-08 influenza season," said Linda Peters, senior vice president of regulatory affairs at MedImmune.

FluMist reached the market for the 2003-04 season with much fanfare as a product that would be welcomed by people who didn't like being stuck with needles. But its high price, the lack of reimbursement support from many managed care organizations, cumbersome storage required by pharmacies and the narrow scope of the vaccine's coverage contributed to FluMist being an expensive disappointment.

Although the company has kept FluMist on the market, it has made and sold comparatively few doses vs. conventional flu vaccines. MedImmune is counting on the new version, called CAIV-T, to revive its vaccine sales.

Like FluMist, CAIV-T is designed for healthy people from the ages of 5 to 49. However, the most vulnerable patients are those above and below the range. MedImmune said it plans to ask the FDA in the next few weeks to approve an expanded label for FluMist, based on a clinical study of 8,500 children aged 6 months to 59 months. Peters added that the company plans to market CAIV-T during the 2007-08 season to people as young as 12 months.

In early-afternoon trading, MedImmune's stock was off 15 cents to $25.79.