Novavax Inc. announced Feb. 9 new data from a clinical study that began in May among healthy adults 18 to 49 years old with Novavax's trivalent seasonal influenza virus-like particle (VLP) vaccine.
The vaccine matched the influenza strains recommended for the 2008-09 influenza season including H1N1 A/Brisbane/59/2007, H3N2 A/Brisbane/10/2007 and B/Florida/04/2006 strains. The study enrolled 241 subjects, including 221 who were randomized to receive either VLP vaccine at 15 micrograms or 60 mcg doses or a placebo and 20 subjects who received a licensed inactivated influenza vaccine (TIV).
Novavax reported safety and hemagglutination inhibition antibody titers from this study in a poster presentation at the 47th Annual Meeting of the Infectious Diseases Society of America.
(Merriam-Webster defines titer as the dilution of a serum containing a specific antibody at which the solution just retains a specific activity (as neutralizing or precipitating an antigen) that it loses at any greater dilution.)
In addition to the HAI titers, functional antibody against the neuraminidase enzyme was measured in the sera of immunized subjects using a neuraminidase inhibition assay (NAI) developed by Novavax scientists. Inhibition of neuraminidase activity may be important in reducing the spread of influenza virus down the respiratory tract and severe influenza disease.
Because neuraminidase mutates less rapidly than hemagglutinin (HA), the antibody against neuraminidase may be more effective in protecting against drifted seasonal strains or new, emerging strains of influenza virus.
In continued evaluation of the clinical study, Novavax tested volunteers for NAI against H3N2/Brisbane and B/Florida components of the vaccine before and after immunization. The results showed that 50 percent to 73 percent of the volunteers immunized with the Novavax VLP vaccine had a fourfold increase in the antibody that blocks neuraminidase activity. In contrast, only one of 19 volunteers who received the TIV showed a fourfold rise for NAI. There was no fourfold rise in volunteers that received placebo.
"These are very exciting results which not only support continued development of novel VLP vaccines against influenza but also provides a cornerstone to potentially differentiate our vaccine from the current standard of care," said Dr. Rahul Singhvi, president and CEO of Novavax.
"We will continue to evaluate NAI responses in additional clinical trials particularly in the ongoing study in the elderly and work to optimize the NA activity required in our vaccine to maximize NAI responses. We believe these new data reinforce our long-standing thesis that VLP influenza vaccines have the potential to induce broad immunity that could lead to meaningful reduction in the burden of disease."