MF59-Adjuvanted Seasonal Trivalent Inactivated Influenza Vaccine: Safety and Immunogenicity in Young Children at Risk of Influenza Complications

Abstract Objective To assess safety and immunogenicity of the MF59 ® -adjuvanted seasonal trivalent inactivated influenza vaccine (aIIV3; Fluad™) in children aged 6 months through 5 years who are at risk of influenza complications. Methods A retrospective analysis was performed to examine unsolicited adverse events (AEs) in an integrated data set from 6 randomized clinical studies that compared aIIV3 with nonadjuvanted inactivated influenza vaccines (IIV3). The integrated safety set comprised of 10,784 children, of which 373 (3%) were at risk of influenza complications. Results The at-risk safety population comprised 373 children 6 months through 5 years of age: 179 received aIIV3 and 194 received nonadjuvanted IIV3 (128 subjects received a licensed IIV3). The most important risk factors were include respiratory system illnesses (62% to 70%), or infectious and parasitic diseases (33% to 39%). During the treatment period, unsolicited AEs occurred in 54% of at-risk children and 55% of healthy children who received aIIV3; of those receiving licensed IIV3, 59% of at-risk and 62% of healthy subjects reported an unsolicited AE. The most common AEs were infections, including upper respiratory tract infection. Serious AEs (SAEs) were reported in Conclusion In young children at risk of influenza complications, aIIV3 was well-tolerated and had a safety profile that was generally similar to that of nonadjuvanted IIV3. Similar to the not-at risk population, the immune response in at-risk subjects receiving aIIV3 was increased over those receiving IIV3, suggesting aIIV3 is a valuable option in young children at risk of influenza complications.