MedImmune says chilled flu vaccine works as well as frozen

Jun 23, 2005 (CIDRAP News) A refrigerated form of MedImmunes FluMist intranasal influenza vaccine has been shown to be as effective as the standard frozen form in stimulating the immune system, the company says.

Preliminary results from a randomized, double-blind, phase 3 bridging study involving 980 people at 26 US sites show comparable immune responses for the frozen formulation already on the market and the refrigerated vaccine, according to a MedImmune news release.

A Washington Post report said the need to store FluMist in a freezer has hindered widespread adoption of the nasal spray vaccine. Standard flu shots are stored in refrigerators, and the need for freezer storage causes inconvenience for many clinics, the story said.

The study involved 414 children aged 5 to 8 years who received two doses of vaccine and 566 children 9 and older who received one dose of vaccine. Immunogenicity was assessed by measuring antibody levels in the blood serum for each of the three strains in the vaccine. Before participants received their first dose of vaccine, investigators took serum samples. They repeated the step 28 to 35 days after the last dose of vaccine.

The results show that the refrigerated vaccine, called cold adapted influenza vaccine, trivalent (CAIV-T), prompted post-vaccination antibody levels for all three flu strains that were equivalent to those induced by the frozen formulation of FluMist, MedImmune said. The news release did not list the specific antibody levels.

The study results will allow MedImmune to seek Food and Drug Administration (FDA) approval for CAIV-T in healthy people aged 5 to 49, said Edward M. Connor, MD, executive vice president and chief medical officer for the company. Approval will allow the company to replace the frozen version of the vaccine in the marketplace.

The Post reported that MedImmune will seek federal approval for CAIV-T for the 2007-08 flu season.

Other studies are under way to compare the immunogenicity of CAIV-T with that of injectable flu vaccine in children aged 6 months to 5 years, Connor said. The Post said the intranasal vaccine could have a competitive edge over injected vaccines in this age-group.

The frozen FluMist vaccine has been licensed for use in healthy people aged 5 to 49 since June 2003. Americans used about 2 million doses of FluMist this past flu season, the Post report said.

Editor's note: The University of Minnesota Center for Infectious Disease Research and Policy (CIDRAP), publisher of this Web site, participated in a MedImmune-sponsored, school-based intervention study of FluMist in children in the past year.