MedImmune, Inc. has announced clinical data showing that a live, attenuated intranasal
influenza vaccine (LAIV) may help induce broader immunity in children against drifted influenza strains when compared to the traditional flu shot (TIV). The data will be presented on May 2, 2004 at the annual meeting of the
Pediatric Academic Societies (PAS) in San Francisco, California. The associated PAS abstract is entitled “Cross-Reactive
Antibody Response to a Live-Attenuated Influenza Vaccine in Children Against Influenza A/H3N2 Fujian-Like Strains.”
“We are building a body of evidence to determine whether live, attenuated intranasal flu vaccine technology may offer certain advantages over the traditional injectable flu vaccine, particularly in children,” said Dr. Paul Mendelman, vice president of clinical development, MedImmune Vaccines, who will present the data at PAS.
In 2003, the U.S. Food & Drug Administration approved MedImmune’s FluMist™ (Influenza Virus Vaccine Live, Intranasal) as the first live, attenuated intranasal vaccine to prevent the flu. The company is also developing the next generation of FluMist, known as CAIV-T, which is the subject of the PAS abstract.
Phase 2 Clinical Trial Results
Each year the U.S. Public Health Service and the World Health Organization (WHO) select the three influenza strains that are represented in each manufacturer’s flu vaccines. For the 2003/2004 season, the A/Panama/H3N2 strain chosen for production of both FluMist and injectable flu vaccines did not optimally match the drifted Fujian-like H3N2 strains that widely circulated and caused substantial influenza disease in the U.S.
To evaluate the ability of a live, attenuated influenza vaccine to protect against this drifted strain, MedImmune analyzed blood samples collected from approximately 50 healthy children, 6-36 months of age, who received a single dose of either CAIV-T or TIV containing the A/Panama/H3N2 strain. Antibody responses to the A/Panama vaccine strain and A/Fujian-like drift variant were significantly higher in children vaccinated with CAIV-T than in children receiving TIV. These responses suggest that a single dose of the live-attenuated vaccine induces broader immunity when compared to the injectable vaccine, and, therefore, could provide more protection against strains contained within the vaccine as well as drifted variants.
These data are consistent with previous information that showed FluMist to be highly effective against a drifted variant A/Sydney/H3N2 in both children and adults during the 1997/1998 influenza season.
FluMist is the first live, attenuated influenza vaccine indicated for active immunization for the prevention of disease caused by influenza A and B viruses in healthy children and adolescents, 5 to 17 years of age, and healthy adults, 18 to 49 years of age.
There are risks associated with all vaccines, including FluMist. FluMist does not protect 100 percent of individuals vaccinated. FluMist is not indicated for immunization of individuals less than 5 years of age, or 50 years of age and older. Currently it is unknown whether FluMist will conclusively provide protection against circulating drifted strains.