H5N1 Avian Flu Vaccine Shows Promise in Trials
Phase I trial results showed vaccine was safe and produced immune response
THURSDAY, May 11 (HealthDay News) -- Phase I trials of a vaccine against the pathogenic avian influenza A virus H5N1 have shown that it is well-tolerated and produces an immune response sufficient for it to meet European vaccine licensing requirements, according to a study published online May 11 in The Lancet.
Melanie Saville, M.B.B.S., of Sanofi Pasteur, Marcy l'Etoile, France, and colleagues conducted a randomized, open-label, non-controlled phase I trial in 300 volunteers aged 18 to 40 years who were assigned one of six inactivated split influenza A/Vietnam/1194/2004 (H5N1) influenza vaccine formulations. The six formulations were 7.5 μg, 15 μg and 30 μg with or without aluminium hydroxide adjuvant. The vaccinations were given on days 0 and 21 and blood samples taken on days 0, 21 and 42.
There were no serious adverse events for any of the formulations, few severe reactions and no oral temperatures above 38 degrees Celsius. An immune response was triggered by all formulations, in some cases after one dose. The best response was elicited by the adjuvanted 30 μg formulation. Two doses of the non-adjuvanted 7.5 μg, adjuvanted 15 μg or non-adjuvanted 15 μg all had a seroconversion rate of more than 40 percent.
"In a pandemic situation, the aim will be to immunize a maximum number of people," the authors note, and caution that the level of post-vaccination antibodies needed to achieve protection is not yet known.