Comparability of Titers of Antibodies against Seasonal Influenza Virus Strains as Determined by Hemagglutination Inhibition and Microneutralization Assays.

We compared titers of antibodies against A/H1N1, A/H3N2, and B influenza virus strains collected pre- and postvaccination using hemagglutination inhibition (HI) and microneutralization (MN) assays and data from two vaccine trials: study 1, performed with a cell-grown trivalent influenza vaccine (TIVc) using cell-grown target virus in both assays, and study 2, performed with an egg-grown adjuvanted quadrivalent influenza vaccine (aQIVe) using egg-grown target virus. The relationships between HI- and MN-derived log-transformed titers were examined using different statistical techniques. Deming regression analyses showed point estimates for slopes generally close to 1 across studies and strains. The slope of regression was closest to 1 for A/H3N2 strain when either cell- or egg-grown viral target virus was used. Bland-Altman plots indicated a very small percentage of results outside 2 and 3 standard deviations. The magnitudes and directions of differences between titers in the two assays varied by study and strain. Mean differences favored the MN assay for A/H1N1 and B strains in study 1, whereas the titers determined by HI were higher than those determined by MN against the A/H3N2 strain. In study 2, mean differences favored the MN assay for A/H3N2 and B strains. Overall, the directions and magnitudes of the mean differences were similar between the two vaccines. The concordance correlation coefficient values ranged from 0.74 (A/H1N1 strain, study 1) to 0.97 (A/H3N2 strain, study 1). The comparative analysis demonstrates an overall strong positive correlation between the HI and MN assays. These data support the use of the MN assay to quantify the immune response of influenza vaccines in clinical studies, particularly for the A/H3N2 strain.

A phase 1, randomized, observer blind, antigen and adjuvant dosage finding clinical trial to evaluate the safety and immunogenicity of an adjuvanted, trivalent subunit influenza vaccine in adults ≥ 65 years of age.

OBJECTIVE: To assess the safety and immunogenicity of the MF59®-adjuvanted trivalent influenza vaccine (aTIV; Fluad®) compared with modified aTIV formulations. METHODS: A total of 196 subjects ≥ 65 years were randomized to receive7different formulations of vaccine containing a range of adjuvant and antigen dosesby single injection, or divided into two injections at a single time point. The primary study objective was to compare the serologic response of different formulations of aTIV containing increased amounts of adjuvant and antigen21 days after vaccination. Subjects were followed for immunogenicity and safety for one year. RESULTS: The highest immune response, as measured by hemagglutination inhibition (HI) assay, 3 weeks after vaccination was observed in subjects in Group 6 with GMT 382.2 (95% confidence interval [CI] 237.5 to 615.0), 552.3 (364.8 to 836.1), and 54.1 (36.9 to 79.4) against A/H1N1, A/H3N2, and B respectively. Rates of seroconversion were also generally highest in this treatment group: 75% (95% CI 55.1 to 89.3), 75% (55.1 to 89.3), and 42.9% (24.5 to 62.8), respectively, against A/H1N1, A/H3N2, and B strains. The highest incidence of solicited adverse events (AEs) was reported by subjects who received both the highest dosage of antigen in combination with the highest dosage of adjuvant at the same site: 67.9% and 57.1% in Groups 4 and 6, respectively. The majority of solicited AEs were mild to moderate in severity. The number of unsolicited AEs was similar across the different dosages. CONCLUSION: In this phase I trial of adults ≥ 65 years of age who received increased adjuvant and antigen dosages relative to the licensed aTIV, increased dosage of MF59 resulted in increased immunogenicity against all 3 components of seasonal influenza vaccine. The increase in immunogenicity was accompanied by an increase in the incidence of local reactogenicity.