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).  Inhibition of neuraminidase activity may be important in reducing the spread and severity of influenza infection.  Novavax tested volunteers for NAI against B/Florida, H3N2/Brisbane and H1N1/Brisbane components of the vaccine before and after immunization.  Against the B strain, 59% of the patients receiving the 15 mcg dose of VLP showed a 4-fold or higher rise in NAI titers over pre-immune levels.  At the 60 mcg VLP dose, 73% had a 4-fold rise while only one subject (5%) from the TIV population had a 4-fold rise.  In the NAI assay against the H3N2 strain, 50% of the patients immunized with the 15 mcg VLP dose had a 4-fold rise in NAI titers.  At the 60 mcg VLP dose, 56% had a 4-fold rise.  In the small subset of subjects tested against H1N1 NAI activity (10 placebo and 20 at the 60 mcg VLP dose), the NAI in the VLP treated group increased about 30% over preimmunization levels while the placebo treated group had no increase over pre-immunization levels.

"The data released today show that our VLP influenza vaccine not only induces a robust HAI response but also enhances the NAI response far above that induced by TIV," said Dr. Rahul Singhvi, President and Chief Executive Officer of Novavax. "We will continue measurement of NAI activity in other clinical trials since we believe that the ability of the VLP vaccine to elicit an NAI response may differentiate our vaccine from others.  These NAI results support our position that VLP influenza vaccines have the potential to induce a broad-based immune response that could lead to improved clinical outcomes.  We now await comparative immunological and safety data from a larger head to head clinical trial in older adults (>60 years of age) between TIV and our VLP vaccine," said Dr. Singhvi.