Immunogenicity of adjuvanted versus high-dose inactivated influenza vaccines in older adults: a randomized clinical trial

BACKGROUND

Adjuvanted inactivated influenza vaccine (aIIV) and high-dose inactivated influenza vaccine (HD-IIV) are U.S.-licensed for adults aged ≥ 65 years. This study compared serum hemagglutination inhibition (HAI) antibody titers for the A(H3N2) and A(H1N1)pdm09 and B strains after trivalent aIIV3 and trivalent HD-IIV3 in an older adult population.

RESULTS

The immunogenicity population included 342 participants who received aIIV3 and 338 participants who received HD-IIV3. The proportion of participants that seroconverted to A(H3N2) vaccine strains after allV3 (112 participants [32.8%]) was inferior to the proportion of participants that seroconverted after HD-IIV3 (130 participants [38.5%]) at day 29 after vaccination (difference, - 5.8%; 95%CI, - 12.9% to 1.4%). There were no significant differences between the vaccine groups in percent seroconversion to A(H1N1)pdm09 or B vaccine strains, in percent seropositivity for any of the strains, or in post-vaccination GMT for the A(H1N1)pdm09 strain. The GMTs for the post-vaccination A(H3N2) and B strains were higher after HD-IIV than after aIIV3.

CONCLUSIONS

Overall immune responses were similar after aIIV3 and HD-IIV3. For the primary outcome, the aIIV3 seroconversion rate for H3N2 did not meet noninferiority criteria compared with HD-IIV3, but the HD-IIV3 seroconversion rate was not statistically superior to the aIIV3 seroconversion rate.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03183908.

Relative effectiveness of the adjuvanted vs non-adjuvanted seasonal influenza vaccines against severe laboratory-confirmed influenza among hospitalized Italian older adults

OBJECTIVES

In this study, we aimed to investigate the relative vaccine effectiveness (rVE) of the MF59-adjuvanted trivalent (aTIV) and non-adjuvanted quadrivalent (QIVe) egg-based standard-dose vaccines against severe laboratory-confirmed influenza.

METHODS

This test-negative case-control study was conducted in a hospital setting during four recent Italian influenza seasons (from 2018/19 to 2021/22). The clinical outcome was severe acute respiratory infection (SARI) with laboratory confirmation diagnosed among subjects aged ≥65 years. rVE of aTIV versus QIVe was estimated through propensity score matching followed by logistic regression.

RESULTS

The influenza virus circulated to a significant extent only during the 2018/19 and 2019/20 seasons. The final population included 512 vaccinated older adults, of which 83 were cases and 429 were test-negative controls. aTIV and QIVe users differed substantially from the point of view of several baseline characteristics. The propensity score adjusted rVE of aTIV vs QIVe was 59.2% (95% CI: 14.6%, 80.5%), 54.7% (95% CI: -28.7%, 84.0%) and 56.9% (95% CI: -7.8%, 82.8%) against any influenza, A(H1N1)pdm09 and A(H3N2), respectively.

CONCLUSION

aTIV was more effective than QIVe in preventing laboratory-confirmed SARI. The benefits of aTIV may be obscured by confounding indication.

Comparative effectiveness of adjuvanted versus high-dose seasonal influenza vaccines for older adults: A systematic review and meta-analysis

OBJECTIVES

MF59-adjuvanted standard-dose and non-adjuvanted high-dose seasonal influenza vaccines have been developed to protect older adults at high risk of severe complications. The aim of this study was to summarize the available evidence on the comparative efficacy/effectiveness of these two vaccines.

METHODS

A systematic literature review (CRD42022313021) of experimental and observational studies was conducted according to the PRISMA guidelines. When possible, the extracted effect sizes were pooled in random-effects meta-analyses.

RESULTS

Ten studies were identified. Of these, no head-to-head randomized controlled trials were identified. All available studies had retrospective cohort design and large sample sizes, were conducted in the United States between 2016/17 and 2019/20 seasons and were at moderate risk of bias. Relative effectiveness estimates were limited to non-laboratory-confirmed clinical endpoints, such as medical encounters including hospitalizations. While most pooled relative effectiveness estimates were close to null, few statistically significant pooled effect sizes were small in magnitude, moved in opposite directions and depended on both the study sponsor and specificity of influenza-related outcomes.

CONCLUSIONS

At current, MF59-adjuvanted standard-dose and non-adjuvanted high-dose vaccines appear to have similar effectiveness in preventing seasonal influenza in older adults and no conclusive recommendations on the preference of one vaccine over another could be drawn.

Importance and value of adjuvanted influenza vaccine in the care of older adults from a European perspective - A systematic review of recently published literature on real-world data

BACKGROUND

There is an urgent need for improved influenza vaccines especially for older adults due to the presence of immunosenescence. It is therefore highly relevant to compare enhanced influenza vaccines with traditional influenza vaccines with respect to their effectiveness.

OBJECTIVE

To compare vaccine efficacy and effectiveness of adjuvanted influenza vaccines (aTIV/aQIV) vs. non-adjuvanted standard-dose (TIV/QIV) and high-dose (TIV-HD/QIV-HD) influenza vaccines regarding influenza-related outcomes in older adults, complementing findings from the European Centre for Disease Prevention and Control (ECDC)'s systematic review of enhanced seasonal influenza vaccines from February 2020.

METHODS

A systematic literature search was conducted in Embase and MEDLINE to identify randomised controlled trials, observational studies and systematic reviews, published since ECDC's systematic review (between 7 February 2020 and 6 September 2021). Included studies were appraised with either the Cochrane Risk of Bias tool, ROBINS-I or AMSTAR 2.

RESULTS

Eleven analyses from nine real-world evidence (RWE) studies comprising ∼53 million participants and assessing the relative vaccine effectiveness (rVE) of aTIV vs. TIV, QIV and/or TIV-HD in adults aged ≥65 years over the 2006/07-2008/09 and 2011/12-2019/20 influenza seasons were identified. Nine analyses found that aTIV was significantly more effective than TIV and QIV in reducing influenza-related outcomes by clinical setting and suspected influenza outbreaks (rVE ranging from 7.5% to 25.6% for aTIV vs. TIV and 7.1% to 36.3% for aTIV vs. QIV). Seven analyses found similar effectiveness of aTIV vs. TIV-HD in reducing influenza-related medical encounters, inpatient stays and hospitalisations/emergency room visits. In three analyses, aTIV was significantly more effective than TIV-HD in reducing influenza-related medical encounters and office visits (rVE ranging from 6.6% to 16.6%). Risk of bias of identified studies was moderate to high.

CONCLUSIONS

Our study suggests that both adjuvanted and high-dose vaccines are effective alternatives for vaccination programmes in older adults and preferable over conventional standard-dose vaccines.

Fc functional antibody responses to adjuvanted versus unadjuvanted seasonal influenza vaccination in community-dwelling older adults

BACKGROUND

Seasonal influenza vaccination with a standard trivalent influenza vaccine (TIV) induces a modest, and cross-reactive, Fc functional antibody response in older adults. Recent improvements to influenza vaccines include a quadrivalent influenza vaccine (QIV) and a TIV adjuvanted with the squalene-based oil-in-water emulsion MF59.

METHODS

Pre- and post-vaccination serum samples from older adults vaccinated with QIV (n = 27) and adjuvanted TIV (n = 44) were studied using hemagglutination inhibition (HAI) assays and dimeric Fc-gamma receptor IIIa binding ELISAs, as a surrogate of antibody-dependent cellular cytotoxicity (ADCC).

RESULTS

We found that the unadjuvanted QIV elicited a stronger HAI response against the H1N1 vaccine virus than the adjuvanted TIV. Post-vaccination levels of HA-specific ADCC antibodies were similar for older adults vaccinated with QIV and adjuvanted TIV. The ADCC response to influenza vaccination was largely determined by pre-vaccination or baseline levels of these antibodies, with older adults with low baseline levels of ADCC activity demonstrating greater post-vaccination rises.

CONCLUSIONS

In this cohort of community-dwelling older adults, the QIV was at least as good as the adjuvanted TIV in the induction of ADCC and HAI responses. Further studies on how these antibody responses translate to efficacy in preventing influenza infections are warranted.