Live attenuated influenza vaccine

Abstract

The development of the live, attenuated influenza vaccine (LAIV), based on the cold-adapted (ca), attenuated ca A/Ann Arbor/6/60 and ca B/Ann Arbor/1/66 backbones, has spanned several decades. The vaccine contains three vaccine strains, two attenuated influenza A strains and one attenuated influenza B strain; these vaccine strains are genetic reassortants, each harboring two gene segments from the currently circulating wild type virus conferring the appropriate antigens (e.g., A/H3N2, A/H1N1 or B) and the remaining six gene segments of the live, attenuated influenza A or influenza B donor virus. Both donor viruses have complex genetic signatures that control the key biological traits of the resulting genetic reassortants, including temperature-sensitivity in vitro and attenuation in an animal model, and the overall attenuation of the vaccine. Studies in humans have demonstrated that the attenuated vaccine strains can elicit humoral antibodies as well as cellular immunity; both responses are generally more readily detectable in children than in adults. A number of different clinical studies in children and adults have shown that this vaccine can reduce the burden of influenza illness in vaccinated subjects, including seasons in which the circulating wild type strain has antigenically drifted from the antigens included in the vaccine. These attributes of the live vaccine, as well as others including the ability to produce substantially more vaccine doses per egg than inactivated influenza vaccine make it a potentially useful platform to generate an effective vaccine, to combat both annual seasonal influenza and future influenza pandemics. © Springer Basel AG 2011.