Immunogenicity and safety of quadrivalent versus trivalent inactivated influenza vaccine: a randomized, controlled trial in adults

Abstract

Background: Two phylogenetic lineages of influenza B virus coexist and circulate in the human population (B/Yamagata and B/Victoria) but only one B-strain is included in each seasonal vaccine. Mismatch regularly occurs between the recommended and circulating B-strain. Inclusion of both lineages in vaccines may offer better protection against influenza.

Methods: This study (NCT00714285) assessed the immunogenicity and safety of two candidate quadrivalent influenza vaccines (QIV) containing two A- and two B-strains (one from each lineage) in adults (18-60 years). Subjects were randomized and stratified by age to receive either QIV (non-adjuvanted or low-dose adjuvanted [LD QIV-AS]) or trivalent influenza vaccine (TIV, non-adjuvanted or low-dose adjuvanted [LD TIV-AS]), N = 105 in all treatment groups. The study evaluated the statistical non-inferiority of the immunological response elicited by QIV and LD QIV-AS versus TIV and LD TIV-AS and the statistical superiority of the response elicited by the quadrivalent vaccines against the B-strain (B/Jiangsu) not included in the TIV.

Results: Pre-defined non-inferiority and superiority criteria were reached for both QIVs compared to the TIVs. On Day 21 in all vaccine groups SCRs were ≥54.8%, SPRs ≥88.5% and SCFs ≥5.4 for the A strains and B strain included in all vaccines (B/Malaysia). This fulfilled the European (CHMP) and the US (CBER) licensing criteria for the assessment of influenza vaccines in adults (CHMP criteria: SCR > 40%, SPR > 70%, SCF > 2; CBER criteria: LL of 95% CI for SPR ≥ 70% or SCR ≥ 40%). Only the QIVs met the CHMP and CBER criteria for the B/Jiangsu strain. In the QIV and LD-QIV-AS groups, the SCFs were 9.1 and 8.1, respectively and the SPRs were 98.1% and 95.2%, whereas for the TIV and LD-TIV-AS groups, the SCFs were 2.3 and 2.5, respectively, and the SPRs were 75.0% and 63.8%, with the LLs of the 95% CI <70% for SPR and <40% for SCR.

Conclusions: Addition of a fourth strain did not impact the immune response elicited by the three original strains contained in the TIV. A clear immunological benefit was seen with the QIV formulation for the second B-strain, indicating that quadrivalent vaccines could provide broader protection against influenza.

Trial registration: ClinicalTrials.gov: NCT00714285.

Figure 1

Participant flow diagram. Abbreviations: N = number of participants; LD QIV-AS = low-dose of quadrivalent influenza vaccine adjuvanted with AS03; LD TIV-AS = low-dose of trivalent influenza vaccine adjuvanted with AS03; QIV = quadrivalent influenza vaccine; TIV = trivalent influenza vaccine; TVC = total vaccinated cohort No participants were withdrawn due to SAEs.

Figure 2

Adjusted GMT ratios on Day 21 (ATP cohort for immunogenicity). Adjusted GMT ratios for A/Solomon Islands, A/Wisconsin, B/Malaysia and B/Jiangsu (only included in QIV formulations) on Day 21 for all treatment groups in the per-protocol cohort for immunogenicity. The margin for superiority of response was if the 95% CI lower limit was ≥1 and the margin for non-inferiority of response was if the 95% CI lower limit was ≥0.67. The data points represent the adjusted GMT ratio for QIV group over the TIV group (QIV/TIV; diamond) or the LD QIV-AS group over the LD TIV-AS group (LD QIV-AS/LD TIV-AS; square) with their associated 95% confidence intervals (CIs). Abbreviations: LD QIV-AS: low-dose adjuvanted quadrivalent influenza vaccine; LD TIV-AS: low-dose adjuvanted trivalent influenza vaccine; QIV: quadrivalent influenza vaccine; TIV: trivalent influenza vaccine.

Figure 3

Summary of results of microneutralizing antibody assay for B influenza strains. Note: Seroconversion rates (SCRs) of the microneutralizing antibody assay in all treatment groups. Neutralizing antibody responses to B/Malaysia and B/Jiangsu were measured before vaccination (Day 0, Pre) and 21 days post-vaccination (Day 21, Post). SCRs, defined as ≥4-fold increase in titer relative to the value noted at baseline, are presented with the associated 95% CI. Abbreviations: LD QIV-AS: low-dose adjuvanted quadrivalent influenza vaccine; LD TIV-AS: low-dose adjuvanted trivalent influenza vaccine; QIV: quadrivalent influenza vaccine; TIV: trivalent influenza vaccine.