SAN FRANCISCO — An experimental refrigerator-stable formulation of the live attenuated influenza vaccine marketed as FluMist was comparable to the approved frozen formulation in a phase III trial presented in a poster at the annual meeting of the Pediatric Academic Societies.
Dr. Stan L. Block reported that the two intranasal FluMist formulations had equivalent immunogenicity against three influenza strains (two type A and one type B). Seroresponse rates and reactogenicity events were comparable in the randomized, double-blind study.
Diarrhea, upper abdominal pain, and nausea were the most frequently reported adverse events. All occurred in less than 5% of patients, regardless of formulation. No serious side effects were attributed to either version of the live attenuated influenza vaccine.
The new formulation has two advantages over the approved FluMist, according to Dr. Block, who is in private practice in Bardstown, Ky. It is administered in a smaller volume, and physicians can store it in a refrigerator.
The immunogenicity trial was conducted at 26 U.S. sites from July 2004 to May 2005. Investigators randomized 981 subjects, of whom 942 could be evaluated for safety and 878 for immunogenicity. The latter analysis included 332 children aged 5–8 years and 546 subjects aged 9–49 years.
None of the younger children had been vaccinated before. They received two doses of FluMist, 46–60 days apart. Participants 9 years of age and older received one dose. The dose used with the new formulation was 0.2 mL (0.1 mL in each nostril) vs. 0.5 mL (0.25 mL in each nostril) with the approved formulation.
FluMist manufacturer MedImmune Inc. of Gaithersburg, Md., sponsored the study. MedImmune is seeking approval of the new formulation for use in healthy children aged 6–59 months as well as in healthy children and adults aged 5–49 years, for whom the original formulation was approved in 2003.
The two intranasal FluMist formulations had equivalent immunogenicity against three influenza strains. DR. BLOCK