| Both inactivated influenza vaccine and LAIV are available to reduce the risk of influenza infection and illness. However, the vaccines also differ in key ways (Table 3).
Major Similarities
LAIV and inactivated influenza vaccine contain strains of influenza viruses that are antigenically equivalent to the annually recommended strains: one influenza A (H3N2) virus, one A (H1N1) virus, and one B virus. Each year, one or more virus strains might be changed on the basis of global surveillance for influenza viruses and the emergence and spread of new strains. Viruses for both vaccines are grown in eggs. Both vaccines are administered annually to provide optimal protection against influenza infection (Table 3).
Major Differences
Inactivated influenza vaccine contains killed viruses, whereas LAIV contains attenuated viruses still capable of replication. LAIV is administered intranasally by sprayer, whereas inactivated influenza vaccine is administered intramuscularly by injection. LAIV is more expensive than inactivated influenza vaccine. LAIV is approved for use only among healthy persons aged 5–49 years; inactivated influenza vaccine is approved for use among persons aged >6 months, including those who are healthy and those with chronic medical conditions (Table 3).
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