Gastrointestinal Events in High-Dose vs Standard-Dose Influenza Vaccine Recipients.

Passive surveillance data had signaled the possibility of gastrointestinal adverse events occurring after the administration of high-dose inactivated influenza vaccine (IIV-HD). However, in a large, prospective randomized clinical trial, rates of serious gastrointestinal events were no greater among IIV-HD recipients than among those who received a standard-dose influenza vaccine.

Fluzone® Intradermal Quadrivalent Influenza Vaccine.

INTRODUCTION: An intradermal version of Fluzone® split-virion inactivated trivalent influenza vaccine, containing 9 µg hemagglutinin per strain of A/H1N1, A/H3N2, and one B lineage virus (Fluzone Intradermal, Sanofi Pasteur), became available in the US during the 2011-2012 influenza season for adults 18-64 years of age. In advance of the 2015-2016 season, Fluzone Intradermal was replaced with Fluzone Intradermal Quadrivalent vaccine, which contains 9 µg hemagglutinin per strain of the two A-strain viruses and both B-strain lineage viruses (Victoria and Yamagata). AREAS COVERED: This literature review summarizes the history and mechanism of intradermal vaccination, discusses the clinical trial results supporting the immunogenicity and safety of Fluzone Intradermal Quadrivalent vaccine, and describes the unique microinjection system used to deliver Fluzone Intradermal Quadrivalent. Expert commentary: Fluzone Intradermal Quadrivalent may boost confidence in influenza vaccination with the addition of a second B-lineage strain. By using an innovative microinjection system, the vaccine is also designed to address some of the logistic challenges faced by healthcare providers administering immunizations.

Correlates of Protection against Influenza in the Elderly: Results from an Influenza Vaccine Efficacy Trial.

Although a number of studies have investigated and quantified immune correlates of protection against influenza in adults and children, data on immune protection in the elderly are sparse. A recent vaccine efficacy trial comparing standard-dose with high-dose inactivated influenza vaccine in persons 65 years of age and older provided the opportunity to examine the relationship between values of three immunologic assays and protection against community-acquired A/H3N2 influenza illness. The high-dose vaccine induced significantly higher antibody titers than the standard-dose vaccine for all assays. For the hemagglutination inhibition assay, a titer of 40 was found to correspond with 50% protection when the assay virus was antigenically well matched to the circulating virus--the same titer as is generally recognized for 50% protection in younger adults. A dramatically higher titer was required for 50% protection when the assay virus was a poor match to the circulating virus. With the well-matched virus, some protection was seen at the lowest titers; with the poorly matched virus, high levels of protection were not achieved even at the highest titers. Strong associations were also seen between virus neutralization test titers and protection, but reliable estimates for 50% protection were not obtained. An association was seen between titers of an enzyme-linked lectin assay for antineuraminidase N2 antibodies and protection; in particular, the proportion of treatment effect explained by assay titer in models that included both this assay and one of the other assays was consistently higher than in models that included either assay alone. (This study has been registered at ClinicalTrials.gov under registration no. NCT01427309.).

Safety and immunogenicity of an inactivated quadrivalent influenza vaccine in children 6 months through 8 years of age.

BACKGROUND: Strains of 2 distinct influenza B lineages (Victoria and Yamagata) have cocirculated in the United States for over a decade, but trivalent influenza vaccines (TIVs) contain only 1 B-lineage strain. Each season, some or most influenza B disease is caused by the B lineage not represented in that season's TIV. Quadrivalent influenza vaccines (QIVs) containing a strain from each B lineage should resolve this problem. METHODS: This was a Phase III, randomized, multicenter trial in the United States among children 6 months to <9 years of age to evaluate the safety and immunogenicity of inactivated QIV compared with inactivated control TIVs containing opposite B-lineage strains. Participants were randomized at a ratio of approximately 4:1:1 to receive QIV, TIV containing a Victoria-lineage B strain or TIV containing a Yamagata-lineage B strain. Sera were collected pre- and 28-days post-final vaccination and safety was assessed for 6 months after the last injection. RESULTS: A total of 4363 participants were enrolled. QIV induced noninferior antibody responses to all A strains and corresponding B strains compared with the control TIVs and superior antibody responses to the noncorresponding B strain in each TIV. Rates of solicited reactions and unsolicited and serious adverse events were similar in all groups. CONCLUSIONS: This study demonstrated that QIV is safe and immunogenic among children 6 months to <9 years of age. These findings, along with data from 2 other studies of this QIV in adults, suggest that QIV should offer protection against both B lineages with a safety profile similar to TIV across all ages.