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. 2024 Oct 11;12(10):1161.
doi: 10.3390/vaccines12101161.

Modelling the Relative Vaccine Efficacy of ARCT-154, a Self-Amplifying mRNA COVID-19 Vaccine, versus BNT162b2 Using Immunogenicity Data

Van Hung Nguyen  1 , Pascal Crépey  2 , Jean Marie Pivette  3 , Ethan Settembre  4 , Sankarasubramanian Rajaram  5 , John Youhanna  4 , Aimee Ferraro  4 , Cheng Chang  4 , Josephine van Boxmeer  6 , Joaquin F Mould-Quevedo  7
Affiliations

Modelling the Relative Vaccine Efficacy of ARCT-154, a Self-Amplifying mRNA COVID-19 Vaccine, versus BNT162b2 Using Immunogenicity Data

Van Hung Nguyen et al. Vaccines (Basel). .

Abstract

Background: Self-amplifying mRNA vaccines have the potential to increase the magnitude and duration of protection against COVID-19 by boosting neutralizing antibody titers and cellular responses. Methods: In this study, we used the immunogenicity data from a phase 3 randomized trial comparing the immunogenicity of ARCT-154, a self-amplifying mRNA COVID-19 vaccine, with BNT162b2 mRNA COVID-19 vaccine to estimate the relative vaccine efficacy (rVE) of the two vaccines over time in younger (<60 years) and older (≥60 years) adults. Results: By day 181 post-vaccination, the rVE against symptomatic and severe Wuhan-Hu-1 disease was 9.2-11.0% and 1.2-1.5%, respectively, across age groups whereas the rVE against symptomatic and severe Omicron BA.4/5 disease was 26.8-48.0% and 5.2-9.3%, respectively, across age groups. Sensitivity analysis showed that varying the threshold titer for 50% protection against severe disease up to 10% of convalescent sera revealed incremental benefits of ARCT-154 over BNT162b2, with an rVE of up to 28.0% against Omicron BA.4/5 in adults aged ≥60 year. Conclusions: Overall, the results of this study indicate that ARCT-154 elicits broader and more durable immunogenicity against SARS-CoV-2, translating to enhanced disease protection, particularly for older adults against Omicron BA.4/5.

Keywords: ARCT-154; BNT162b2; efficacy; older adults; self-amplifying mRNA vaccine.

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Conflict of interest statement

Van Hung Nguyen and Jean Marie Pivette: Employees of VHN Consulting, which received funding from CSL Seqirus for the analysis described in the manuscript and for manuscript development. Pascal Crépey received funding from VHN Consulting for the analysis described in the manuscript. Ethan Settembre, Sankarasubramanian Rajaram, John Youhanna, Aimee Ferraro, Cheng Chang, Josephine van Boxmeer, and Joaquin F. Mould-Quevedo: Employees of CSL Seqirus.

Figures

Figure 1
Figure 1
rVE of ARCT-154 vs. BNT162b2 against symptomatic COVID-19 caused by (a) Wuhan-Hu-1 and (b) Omicron BA.4/5 on days 29, 91, and 181 post-vaccination, by age group. rVE, relative vaccine efficacy.
Figure 2
Figure 2
rVE of ARCT-154 vs BNT162b2 against severe COVID-19 on days 29, 91, and 181 post-vaccination, by age group, including sensitivity analysis varying the threshold titer considered protective against 50% of severe disease from 3% to 10% of convalescent sera. rVE, relative vaccine efficacy.
See this image and copyright information in PMC

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