Intranasal Spray, Live Attenuated Influenza Vaccine

Abstract

The live attenuated influenza vaccine (LAIV) was developed to enhance immunogenicity and improve vaccine acceptance. The influenza virus is attenuated to eliminate pathogenicity while retaining the ability to replicate in the nasal mucosa, thereby inducing both mucosal immunity, particularly immunoglobulin A (IgA), and systemic immunity, including immunoglobulin G (IgG). This vaccine is administered via the intranasal route, providing a convenient method of administration, especially for children and individuals who prefer not to receive injectable vaccines. Clinical studies have demonstrated that LAIV is effective in preventing influenza in both children and adults. In healthy children aged 6–59 months, LAIV has shown superior efficacy to the inactivated influenza vaccine in preventing culture-confirmed influenza. In healthy adults aged 18–64 years, LAIV has demonstrated significant cross-protection against antigenically distinct influenza strains and has been shown to reduce the incidence of severe febrile illness and febrile upper respiratory illness. The most commonly reported adverse events include rhinorrhea, nasal congestion, and sore throat. However, an increased risk of wheezing has been observed in children younger than 2 years of age; therefore, LAIV is not recommended for use in this age group. In addition, LAIV is not recommended for pregnant women and individuals with immunocompromising conditions.