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news.Sanofi Pasteur, the vaccines division of Sanofi-Aventis Group, has announced that an investigational high-dose influenza vaccine demonstrated increased immune responses among adults 65 years of age and older compared with the standard influenza vaccine. The candidate high-dose intramuscular formulation of the influenza vaccine is being developed by Sanofi Pasteur.
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The Phase III study of almost 4,000 people 65 years of age and older compared the high-dose influenza vaccine with the standard inactivated influenza vaccine formulated for the 2006-2007 season. The key finding is that the new high-dose vaccine increased the immune responses to all three influenza strains compared with standard vaccine in the study population, the company said.
An important additional observation was that the increased immune response was also observed in the potentially more vulnerable subset of study participants who had no measurable circulating protective antibodies before receiving their annual influenza vaccine.
In the randomized double-blind study conducted at 30 centers throughout the US, 2,575 people received the high-dose influenza vaccine and 1,262 received the standard influenza vaccine. The standard influenza vaccine contained 15 micrograms of hemagglutinin (HA) of each of three influenza strains, and the high-dose vaccine contained four times as much, 60 micrograms HA per strain. Both vaccines contained two influenza type A strains (H1N1 and H3N2) and one influenza type B strain.
After 28 days, investigators assessed serum hemagglutination inhibition (HAI) titers in study participants, a standard measurement of the immune response to influenza vaccination. HAI titers are thought by researchers to correlate with increased protection against illness after exposure to influenza.
Statistically significant higher HAI titers against all three influenza virus strains were reported in those who received the high-dose vaccine compared with those who received the standard vaccine. Immunogenicity results met pre-defined criteria for overall superiority of the high-dose vaccine, the company said.
In a post hoc analysis, study investigators also examined post-vaccination immune responses induced by the two vaccines among a subgroup of study participants with no protective antibodies (HAI titers less than 1:10 as measured by their pre-vaccination serum sample). Among all study participants, 10% were seronegative for H1N1, 8% were seronegative for H3N2, and 21% were seronegative for the B strain.
Approximately 28 days after vaccination, a higher percentage of the subgroup given the high-dose vaccine developed seroprotective HAI titers of 1:40 or greater to each of the three vaccine strains compared with those given the standard vaccine. In addition, mean HAI titers for all strains were higher in the seronegative individuals who received the high-dose vaccine compared with those who received the standard vaccine.