Live attenuated influenza vaccine

Live attenuated influenza vaccine (LAIV) is a type of influenza vaccine in the form of a nasal spray. It is an attenuated vaccine, unlike most influenza vaccines, which are inactivated vaccines. LAIV is administered intranasally, while inactivated vaccines are administered by intramuscular injection. Both live attenuated and inactivated vaccines are typically trivalent. That is, they contain material from three different influenza virus strains recommended by national and international public health agencies as most likely to be protective against seasonal influenza in any given year. However, for 2013-2014 the FDA has switched to a quadrivalent LAIV. LAIV is sold under the trade name FluMist in the United States and Canada, and Fluenz in Europe.