Live attenuated influenza vaccine.

Cold-adapted Ann Arbor based live attenuated influenza vaccine (LAIV) has been available in the USA since 2003. The vaccine is efficacious against influenza infection. Features of LAIV include: easy administration suitable for mass immunization, cross-reactivity to drifted strains for broader coverage, and establishment of herd immunity for control of influenza spread. Annual seasonal LAIV now contains four strains against influenza A H1N1, H3N2, influenza B-Victoria, and B-Yamagata lineages that are co-circulating in humans. LAIV played a significant role in protecting the public from the 2009 H1N1 pandemic and has been evaluated for pandemic preparedness. Pandemic vaccines including influenza H2, H5, H6, H7, and H9 subtypes have been produced and evaluated in preclinical and small-scale phase I clinical studies. This review summarizes the current status and perspectives of seasonal and pandemic LAIV.