Introducing Modern Recombinant Technology to the Realm of Seasonal Influenza Vaccine: Flublok® For Prevention of Influenza in Adults

Introduction Flublok is the first recombinant hemagglutinin (rHA) vaccine licensed in the US by FDA for the prevention of influenza in adults 18 and older. The rHAs are produced in insect cell culture using the baculovirus expression vector system (BEVS) technology, and are, in contrast to HAs from viruses adapted to growth in hen’s eggs, an exact genetic match to the HAs of the influenza strains selected by World Health Organization and FDA for inclusion in the annual seasonal influenza vaccine. These rHAs can be produced rapidly and in large quantity owing to the universal process across different HAs. This universal production process has been scaled successfully to bioreactors ranging up to 21,000L. This review discusses the immunogenicity, efficacy and safety data derived from five main clinical studies that supported licensure of trivalent Flublok for adults 18 and older in the United States. These data are also under regulatory review in other jurisdictions worldwide, including Japan and Mexico. We show that Flublok results in improved immunogenicity for many influenza strains, likely due to its higher rHA content as compared to conventional inactivated vaccines. Limited data suggest further that efficacy appears to be improved while local reactogenicity is generally less frequent than is observed with conventional inactivated influenza vaccine despite the higher antigen content. Flublok could include rHAs that are designed to mimic “drifted” influenza viruses as techniques improve for predicting emerging antigenic drift. At a minimum, the BEVS system utilized in the Flublok manufacturing process can address late-appearing influenza viruses to which conventional egg-based manufacturing processes cannot respond in a timely fashion. The implementation of this rapid response approach will require collaboration with and support from regulatory authorities.