Preliminary data from a Phase 3 study indicated that CAIV-T ( cold adapted influenza vaccine, trivalent ) showed a statistically significant reduction ( 55 percent ) in influenza illness caused by any influenza strain compared to the injectable influenza vaccine ( TIV ).
The influenza attack rate was 8.6 percent for study participants receiving injectable influenza vaccine compared to 3.9 percent for those who received CAIV-T ( p less than 0.0001 ).

CAIV-T is an investigational, refrigerator-stable formulation of FluMist ( Influenza Vaccine Live, Intranasal ), a frozen vaccine currently approved to prevent influenza in healthy children and adolescents, 5 to 17 years of age, and healthy adults, 18 to 49 years of age.

Pivotal Phase 3 trial for CAIV-T was a randomized, double-blind study designed to assess the safety and relative efficacy of CAIV-T and injectable influenza vaccine in children ages 6 months through 59 months during the 2004-2005 influenza season.

The primary endpoint of the trial was culture confirmed influenza-like illness ( ILI ), based on a modified version of the U.S. Centers for Disease Control & Prevention definition, caused by wild type strains antigenically matched to the vaccine.

CAIV-T showed a 44-percent reduction in the number of these cases, compared to injectable influenza vaccine ( p less than 0.001 ).
For matched strains, the attack rate was 2.4 percent for study participants receiving injectable influenza vaccine compared to 1.4 percent for those receiving CAIV-T ( p less than 0.001 ).

The trial also met its secondary efficacy endpoints, with CAIV-T showing a 58-percent reduction in modified ILI caused by antigenically mismatched wild type strains.
In the case of mismatched strains, the attack rate was 6.2 percent for the injectable influenza vaccine arm and 2.6 percent for the CAIV-T group ( p less than 0.001 ).

The study enrolled 8,492 children and was conducted at 249 sites in 16 countries in North America, Europe and Asia.

The rates of serious adverse events and adverse events were similar in the two groups.
As expected, runny/stuffy nose occurred more frequently in CAIV-T recipients and site of injection events occurred more frequently among injectable influenza vaccine recipients.
In the analyses of medical significant wheezing, the only statistically significant difference was observed in children not previously vaccinated under two years of age after the first dose.
In this analysis, the rate in the CAIV-T arm was 3.2 percent versus 2.0 percent in injectable influenza vaccine recipients. In this same population, no significant difference was observed beyond 42 days after the last vaccination.

Source: MedImmune, 2005


XagenaMedicine2005