A cell culture-derived MF59-adjuvanted pandemic A/H7N9 vaccine is immunogenic in adults.

A potentially deadly A/H7N9 avian-origin influenza virus is currently the cause of an ongoing outbreak in China. Preparedness plans have thus been initiated to preempt the spread of this virus, which appears to have substantial pandemic potential. To effectively prevent a pandemic from unfolding, rapid production of an immunogenic vaccine with an acceptable safety profile is critical. Given the significance to public health, we are reporting immunogenicity and safety results from a phase 1 study in healthy adults administered one of four inactivated A/H7N9 vaccine formulations. Three formulations contained increasing quantities of antigen and of an oil-in-water adjuvant, MF59, and one formulation contained only the maximum dose of antigen without adjuvant. All vaccine formulations were derived using a synthetic virus seed technology in combination with a cell culture approach; together, these techniques have been shown to expedite vaccine production compared to conventional methods. Higher responses were seen with the MF59-adjuvanted versus the nonadjuvanted A/H7N9 vaccine, with significant and potentially protective immune responses after two doses in most subjects with no preexisting immunity to the H7N9 virus. Further, despite increased injection site pain and other mild effects with MF59, all formulations were well tolerated. These encouraging immunogenicity and safety data on the A/H7N9 vaccine provide a strong rationale for further clinical development. By also using synthetic seed/cell culture technology, we are now one step closer to being able to rapidly and reliably respond to a potential H7N9 pandemic using a clinically tested A/H7N9 vaccine.