Live Attenuated Influenza Vaccine (LAIV) Fact Sheet

New York State Department of Health

December 2007

The LAIV has been licensed by the Food and Drug Administration (FDA) since 2003. The LAIV contains live but attenuated (weakened) influenza viruses. It is sprayed into the nostrils rather than injected into the muscle. In September 2007, the FDA approved LAIV for use among healthy children and adults from 2 through 49 years of age. This included those who can spread influenza to people at high risk, such as: household contacts and out-of-home care-takers of infants from 0-23 months of age, health care personnel, and family members, or any one else in close contact with people at risk of serious influenza.

Studies conducted before the licensure of LAIV show that it is protective against influenza disease in both adults and children. Several study findings are summarized below:

  • In one large study conducted among children aged 15-85 months, LAIV reduced cases of influenza illness by 92%. The vaccine also reduced the rate of otitis media with fever by 27% and otitis media with antibiotic use by 28% (CDC, June 2006).
  • In a study conducted with healthy working adults aged 18-64 years, LAIV reduced severe febrile illnesses by 19% and upper respiratory tract illnesses by 24%. LAIV use also was associated with fewer days of illness and of work lost, fewer health-care provider visits, and reduced use of prescription antibiotics and over-the-counter medications (CDC February, 2006).
  • In another study, overall efficacy of LAIV and inactivated influenza vaccine in preventing laboratory-documented influenza was 85% and 71%, respectively. (CDC, June, 2006).
  • One study suggested that LAIV may be more effective than the inactivated vaccine when the strains in the vaccine are not well-matched to the circulating strains causing disease (Belshe, 2000).

Other potential advantages of LAIV include the ease of administration and the acceptability of an intranasal rather than an intramuscular route of administration. Use of LAIV is especially encouraged during shortages of inactivated influenza vaccine because use of LAIV for healthy individuals aged 2-49 years might increase availability of inactivated vaccine for persons in high-risk groups. LAIV can be given to most health care personnel who are 49 years of age or younger who are not pregnant or do not have a medical condition. Only health care personnel who are working with severely immunosuppressed patients during those periods in which the immunosuppressed person requires care in a protective environment cannot receive LAIV. There has never been a documented transmission of the virus from the vaccine in a health care setting.

  • Belshe, RB, et al. Efficacy of vaccination with live attenuated, cold-adapted, trivalent, intranansal influenza virus vaccine against a variant (A/Sydney) not contained in the vaccine. Journal of Pediatrics 2000; 136:168-175.
  • CDC. Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices. MMWR, June, 2006; 55(Early Release): 1-41.
  • CDC. Influenza Vaccination of Health-Care personnel: Recommendations of the Healthcare Infection Control Practices Advisory Committee (HCPAC) and the Advisory committee on Immunization Practices (ACIP). MMWR, February. 2006; 55: RR-2.