Live attenuated influenza vaccine (LAIV) is a type ofinfluenza vaccine in the form of anasal spray that is recommended for the prevention of influenza.[2][7]
In the United States, FluMist is approved for self- or caregiver-administration.[12][13] It is the first influenzavaccine that does not need to be administered by a health care provider.[12]
The live attenuated vaccine is based on aflu strain that does not cause disease, that replicates well at relatively cold temperatures (about 25 °C (77 °F), for incubation purposes), and replicates poorly atbody temperature (which minimizes risk to humans). Genes that code forsurface proteins (targetedantigens) are combined with this host usinggenetic reassortment from strains thatare projected to be circulating widely in the coming months. The resulting viruses are then incubated in chicken eggs and chick kidney cells. To make the refrigerated version, the virus is purified incentrifuges through asucrosegradient, then packaged with sucrose,phosphate,glutamate,arginine, andhydrolyzed piggelatin.[18]
The cold-adapted version of the vaccine is called CAIV-T, and is stable for storage in a refrigerator, rather than requiring freezer storage as did the originally-approved formulation. Approved for the 2007-2008 fluseason,[11] the refrigerated formulation can be distributed more cheaply, making it more price-competitive with injected vaccines. The higher price hampered sales of the original frozen version of FluMist; FluMist was initially priced higher than injectable vaccines, and sold only 500,000 of the fourmillion doses produced its first year on the market, despite a comparative shortage of fluvaccine in fall2004.[22] The price was sharply lowered the next year, and MedImmune reported distributing 1.6million doses in2005.[23] Because of the price drop, despite selling almost threetimes as many doses in2005, the company reported $21million in revenue from FluMist sales,[note 1] compared to $48million the previous year.[25][note 2]
An example of a Flumist home influenza vaccine kit, featuring unpacking and administration instructions, safety warnings, and the box containing the vaccine itself. The kit is shipped in a styrofoam cooler withcold packs to maintain the vaccine at a refrigerated temperature (not shown).
MedImmune is one company that manufactures the live attenuated influenza vaccine, which it sells under the brand name FluMist in the United States, Canada, and Japan,[26] and the brand name Fluenz Tetra in the UK and European Union.[6] For the 2010–2011 fluseason, FluMist was the only live attenuated influenza vaccine approved by theFDA for use in theUS.[27][28] All other FDA-approved lots were inactivated virus vaccines.[citation needed] In September2009, a live attenuated influenza vaccine forthe novel H1N1 influenza virus was approved[29] and the seasonal intranasal vaccine was approved by theEuropean Medicines Agency(EMA) for use in the European Union in 2011.[5] Thequadrivalent vaccine version was approved for use in the European Union in2013.[6]
It was the first and, as of 2007[update], the only live attenuated vaccine for influenza available outside of Europe.[32] In September2009, a live attenuated influenza vaccine for the novelH1N1 influenza virus was approved.[29] In 2011, the vaccine was approved by theEuropean Medicines Agency(EMA) for use in the European Union under the brand name Fluenz.[5][33]
AstraZeneca acquired MedImmune in2007 and retired the MedImmune name.[34][35] In October2024,Time magazine named AstraZenecaFluMist (an "at-home nasal vaccine") as one of the best inventions of2024.[36]
In May2024, theCommittee for Medicinal Products for Human Use(CHMP) of theEuropean Medicines Agency(EMA) adopted a positive opinion, recommending the granting of a marketing authorization for Fluenz, intended for the prevention of influenza disease in children and adolescents.[37][38] The applicant for this medicinal product is AstraZenecaAB.[37]
In September 2024, the USFDA approved FluMist for self- or caregiver-administration. TheFDA granted the approval of FluMist to MedImmuneLLC.[12]
This section needs to beupdated. Please help update this article to reflect recent events or newly available information.(August 2025)
The live attenuated influenza vaccine is designed to be quickly modifiable to present the surface antigens of seasonal flu. This modifiability could also allow it to be quickly customized as a vaccine against apandemic influenza if one were to emerge. In light of theglobal spread of H5N1, ways of reducinghuman mortality in the event of an H5N1 pandemic have been investigated. Modifying FluMist to serve as a specific human H5N1 vaccine is among the measures studied.[39]
In September2006, the USNational Institute of Allergy and Infectious Diseases(NIAID) reported that inoculation with a live attenuated influenza vaccine modified to present surface antigens of certain H5N1 variants provided broad protection against other H5N1 variants inmouse and ferret models.[41] Attenuated live viruses were found protective against H5N1 in mice and chickens in a 2009study.[42]
"Several trials have reported that live attenuated influenza vaccines can boost virus-specific CTLs as well as mucosal and serum antibodies and provide broad cross-protection against heterologous human influenza A viruses." (58, 59)[43] "[V]accine formulas inducingheterosubtypic T cell–mediated immunity may confer broad protection against avian and human influenza A viruses."[43]
^abBlock SL, Yogev R, Hayden FG, Ambrose CS, Zeng W, Walker RE (September 2008). "Shedding and immunogenicity of live attenuated influenza vaccine virus in subjects 5-49 years of age".Vaccine.26 (38):4940–4946.doi:10.1016/j.vaccine.2008.07.013.PMID18662737.
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