[removed]Flublok[/removed], the first trivalent influenza vaccine made using an insect virus (baculovirus) expression system and recombinant DNA technology, was approved last week by the FDA for the prevention of seasonal influenza in people 18 through 49 years of age.

The vaccination, manufactured by Protein Sciences Corp., uses a novel manufacturing technology that allows for production of large quantities of the influenza virus protein, hemagglutinin (HA) – the active ingredient in all inactivated influenza vaccines that is essential for entry of the virus into cells in the body. The majority of antibodies that prevent influenza virus infection are directed against HA, according to the company.

Flublok contains three, full-length, recombinant HA proteins to help protect against two influenza virus A strains, H1N1 and H3N2, and one influenza virus B strain. According to Protein Sciences, Flublok was about 44.6% effective against all circulating influenza strains, not just the strains that matched the strains included in the vaccine, in a study of about 2,500 people who were vaccinated with it.

Flublok has a shelf life of 16 weeks from the date of manufacture. Clinicians are advised to check the expiration date before administering Flublok.