Impact of Variants on Elasomeran Mechanism

How do updated formulations (variants of concern) affect the mechanism of Elasomeran?

Updated mRNA-1273 formulations shift the neutralizing antibody response toward enhanced variant-specific recognition while maintaining the core B cell memory and T cell activation mechanisms of the original vaccine platform, with bivalent versions balancing variant-targeted depth against cross-reactive breadth.

Abstract

Updated mRNA-1273 formulations targeting SARS-CoV-2 variants of concern alter the immune response mechanism through differential neutralizing antibody profiles while maintaining the platform’s core immunological pathways. Monovalent variant-specific vaccines (mRNA-1273.351 targeting B.1.351, mRNA-1273.529 targeting BA.1) demonstrated superior neutralizing antibody responses against their target variants, with geometric mean ratios of 1.67-1.77 for BA.1 formulations and twofold improvements for B.1.351 formulations, but showed reduced cross-reactivity against ancestral strains with fourfold lower neutralization against WA1/2020 D614G. Bivalent formulations (mRNA-1273.211, mRNA-1273.214) balanced this trade-off by maintaining or improving ancestral strain neutralization (GMR 1.11 against D614G for BA.1-bivalent) while achieving GMT ratios ≥1 against all variants of concern tested. All updated formulations induced robust anamnestic B cell memory responses when used as boosters, with variant-modified boosters showing 34.9-61.6 fold increases in neutralization against target variants, restoring immunity that had waned 6-7 fold against wild-type and 24-69 fold against variants over 6 months. Cellular immune mechanisms, including CD4+ and CD8+ T cell responses measured in preclinical models, showed similar activation patterns to the original vaccine, with effector T cell expansion but not effector-memory phenotypes and waning within 6 months. However, longitudinal studies revealed progressive viral escape from updated vaccine-induced immunity, with newer variants continuing to evade even XBB.1.5-updated formulations, indicating that antigenic drift outpaces the vaccine update cycle despite mechanistic improvements in neutralizing breadth and depth.

Methods

We analyzed 10 sources from an initial pool of 200, using 8 screening criteria. Each paper was reviewed for 8 key aspects that mattered most to the research question.

Records from Elicit search

• n = 200

• Papers screened using: Vaccine Type and Formulation, Mechanistic Outcomes, Comparative or Descriptive Data, Study Design, Updated Formulation Focus, Elasomeran Relevance, Mechanistic Data Inclusion, Study Rigor

• n = 200 Papers screened out

• n = 190 Papers included for extraction

• n = 10

Paper search

We performed a semantic search across over 138 million academic papers from the Elicit search engine, which includes all of Semantic Scholar and OpenAlex.

We ran this query: “How do updated formulations (variants of concern) affect the mechanism of Elasomeran?” The search returned 200 total results from Elicit. We retrieved 200 papers most relevant to the query for screening.

Screening

We screened in sources based on their abstracts that met these criteria:

• Vaccine Type and Formulation: Does this study investigate Elasomeran (mRNA-1273, Moderna COVID-19 vaccine) updated formulations specifically designed to target SARS-CoV-2 variants of concern (Alpha, Beta, Gamma, Delta, Omicron, or subsequent WHO-designated variants)?
• Mechanistic Outcomes: Does this study report mechanistic outcomes including immunogenicity, antibody responses, T-cell responses, vaccine efficacy, or molecular mechanisms of action?
• Comparative or Descriptive Data: Does this study provide comparative data between updated formulations and original formulations, other updated formulations, or descriptive mechanistic data on updated formulations?
• Study Design: Is this study a randomized controlled trial, cohort study, case-control study, cross-sectional study, in vitro study, animal study, systematic review, or meta-analysis?
• Updated Formulation Focus: Does this study investigate updated variant formulations (rather than focusing solely on the original Elasomeran formulation without investigation of updated variants)?
• Elasomeran Relevance: Does this study investigate Elasomeran or include comparison to Elasomeran (rather than focusing solely on other COVID-19 vaccines like Pfizer-BioNTech, Johnson & Johnson, or AstraZeneca without Elasomeran investigation)?
• Mechanistic Data Inclusion: Does this study include mechanistic investigation (rather than reporting only safety, adverse events, epidemiological outcomes, or logistical data without mechanistic components)?
• Study Rigor: Is this study a full research article with adequate detail (rather than a case report, case series, editorial, commentary, or conference abstract)?

Data extraction

Updated Formulation:

• Specific vaccine name/code (e.g., mRNA-1273.351, mRNA-1273.211, mRNA-1273.529)
• Variant(s) targeted by the updated formulation (e.g., B.1.351/Beta, BA.1, XBB.1.5)
• Type of formulation (monovalent variant-specific, bivalent original+variant, multivalent)
• Dose amount (e.g., 50 μg, 25 μg)
• How it differs from original mRNA-1273

Immunological Mechanisms

Mechanism type:

Measurement methods: Neutralizing antibodies via pseudovirus neutralization assays (lentivirus-based, VSV-based); live virus focus-reduction neutralization test (FRNT). B cell memory via anamnestic response to boosting. Durability measured at Day 29 and Month 3; up to 6 months post-vaccination.

Results

Characteristics of Included Studies

The systematic review identified 10 sources examining updated mRNA-1273 (Elasomeran) formulations targeting SARS-CoV-2 variants of concern. Full texts were available for 6 studies, while 4 were available as abstracts only.

Synthesis

The findings reveal systematic patterns in how updated mRNA-1273 formulations alter immunological mechanisms, with heterogeneity explained by specific variant targets, formulation strategy (monovalent vs bivalent), and the evolutionary timing of SARS-CoV-2 variants tested.