The study was approved by the independent ethics committee or institutional review board for each institution and conducted in compliance with the standards established by the Declaration of Helsinki, the International Conference for Harmonization guidelines for Good Clinical Practice, and all local and national regulations and directives. mean titers and seroconversion rates were also higher for intramuscular than subcutaneous administration of IIV4-HD. Solicited reactions were more common in participants who received IIV4-HD administered subcutaneously than in those who received IIV4-HD administered intramuscularly or IIV4-SD administered subcutaneously. Unsolicited adverse events were comparable between the vaccine groups, and no safety signals were detected. This study showed that IIV4-HD administered by either intramuscular or subcutaneous injection was well tolerated and highly immunogenic in healthy Japanese adults 65?years of age. Although this study Rabbit Polyclonal to ADRA1A was descriptive, the results add to the evidence that high-dose inactivated influenza vaccines are more immunogenic than standard-dose vaccines in this age group and that intramuscular administration provides greater immunogenicity and lower reactogenicity than subcutaneous administration. strong class=”kwd-title” KEYWORDS: Quadrivalent influenza vaccine, high-dose influenza vaccine, elderly adults, immunogenicity, safety, Japan, intramuscular, subcutaneous Introduction Most influenza-related hospitalizations and deaths occur in adults 65?years of age.1 AescinIIB This appears to be due to increasing comorbidities and waning immune responses associated with aging.2,3 Because of the increased risk, the World Health Organization and most national health authorities recommend that, along with young children, pregnant women, and individuals with certain underlying conditions, adults 65?years of age should be prioritized for influenza vaccination.4 Influenza vaccination is becoming increasingly important in Japan because it has one of the oldest and most rapidly aging populations globally.5 Routine vaccination against influenza was instituted in Japan in 2001 for adults 65?years of age and adults 60C64?years of age with respiratory, cardiac, or renal disease or contamination with human immunodeficiency virus.6,7 Since the 2015/16 season, quadrivalent influenza vaccines have been used to vaccinate eligible individuals in Japan.8 Quadrivalent influenza vaccines contain antigen from two influenza A strains (A/H1N1 and A/H3N2) and both influenza B-strain lineages (Victoria and Yamagata), whereas trivalent vaccines contain the two A strains and a single B-lineage strain. Quadrivalent influenza vaccines were developed to avoid mismatches between the B-strain lineage in trivalent vaccines and the predominant circulating B lineage,9 which occurred in about one-quarter of influenza seasons between 2000 and 2013.10 Switching from trivalent to quadrivalent influenza vaccines in Japan has prevented an estimated 2030 hospitalizations and 98 deaths each year and saved AescinIIB an estimated 10.75 million US dollars from a societal perspective.11 To provide improved protection against influenza infection, a trivalent high-dose, split-virion inactivated influenza vaccine (IIV3-HD; Fluzone? High-Dose, Sanofi Pasteur)12 has been licensed in adults 65?years of age in the US since 2009, Canada since 2015, Australia since 2017, Brazil since 2018, and the United Kingdom since 2019. This vaccine contains 60?g hemagglutinin per influenza strain, which is four times the antigen content of standard-dose influenza vaccines. A multicenter phase III trial in the US and Canada showed that, in adults 65?years of age, IIV3-HD was 24.2% more effective than a standard-dose trivalent influenza vaccine (IIV3-SD) in preventing laboratory-confirmed influenza caused by any strain and 35.4% more effective than IIV3-SD at preventing laboratory-confirmed influenza caused by vaccine-similar strains.13 IIV3-HD is well tolerated in adults 65?years of age, although as expected using the increased antigen dosage, community reactions are more prevalent with IIV3-HD.14 These findings have already been supported by post-marketing research, that have shown that IIV3-HD provides improved safety against influenza, serious pneumonia, post-influenza loss of life, and all-cause, influenza-related, and cardiorespiratory-associated hospitalization.15C19 To improve protection against influenza in older adults, a quadrivalent formulation from the high-dose inactivated influenza vaccine (IIV4-HD) has been developed. A recently available stage III trial in america demonstrated that, in healthful adults 65?years, IIV4-HD was good tolerated and induced defense reactions AescinIIB which were non-inferior to reactions induced by IIV3-HD for the shared strains and first-class reactions for the excess B-lineage stress.20 The existing research, performed in Japan through the 2017C2018 influenza season, compared the safety and immunogenicity of IIV4-HD and standard-dose quadrivalent inactivated influenza vaccine (IIV4-SD) in adults 65?years. In Japan, the typical of look after influenza vaccination can be administration by subcutaneous (SC) shot, whereas the protection and effectiveness of high-dose vaccines possess up to now been demonstrated pursuing intramuscular (IM) shot. In this scholarly study, IIV4-HD was given by both IM and SC shot consequently, whereas IIV4-SD was given by SC shot. Strains contained in influenza vaccines are chosen from the set of World.