Safety and immunogenicity of Sinovac's prototype pandemic influenza H5N1 vaccines: a review on clinical trials.

Sinovac Biotech started to develop prototype pandemic influenza H5N1 vaccines in March 2004. On 2 April 2008, Sinovac's inactivated, aluminium-adjuvanted, whole-virion prototype pandemic influenza A (H5N1) vaccine (PanFlu) was granted production licensure by the China regulatory authority State Food and Drug Administration. The whole-virion H5N1 vaccine was manufactured in embryonated hens' eggs using the reassortant strain NIBRG-14 (A/Vietnam/1194/2004-A/PR/8/34) as vaccine virus. It showed good safety, immunogenicity and cross-reactivity in immunologically naïve adults. In primed adults, the vaccine induced a strong booster response. Plasma from a vaccinated individual showed a beneficial effect following passive immunotherapy of an H5N1 human infection case. This article reviews the process, status and results of clinical evaluation of Sinovac's whole- and split-virion H5N1 vaccines by focusing on the whole-virion vaccine.