# Profiling antibody epitopes induced by mRNA-1273 vaccination and boosters

## TL;DR

This study examines how mRNA-1273 vaccines and boosters affect antibody responses to the SARS-CoV-2 spike protein.

## Contribution

The study identifies specific antibody epitopes and how booster doses, including variant-updated vaccines, influence immune responses.

## Key findings

- Primary vaccination targets multiple S-specific epitopes, with signals declining over time.
- Booster doses after six months revive waning antibody signals and introduce new epitopes.
- Variant-updated booster formulations induce stronger antibody responses than standard boosters.

## Abstract

Characterizing the antibody epitope profiles of messenger RNA (mRNA)-based vaccines against SARS-CoV-2 can aid in elucidating the mechanisms underlying the antibody-mediated immune responses elicited by these vaccines.

This study investigated the distinct antibody epitopes toward the SARS-CoV-2 spike (S) protein targeted after a two-dose primary series of mRNA-1273 followed by a booster dose of mRNA-1273 or a variant-updated vaccine among serum samples from clinical trial adult participants.

Multiple S-specific epitopes were targeted after primary vaccination; while signal decreased over time, a booster dose after >6 months largely revived waning antibody signals. Epitope identity also changed after booster vaccination in some subjects, with four new S-specific epitopes detected with stronger signals after boosting than with primary vaccination. Notably, the strength of antibody responses after booster vaccination differed by the exact vaccine formulation, with variant-updated mRNA-1273.211 and mRNA-1273.617.2 booster formulations inducing significantly stronger S-specific signals than a mRNA-1273 booster.

Overall, these results identify key S-specific epitopes targeted by antibodies induced by mRNA-1273 primary and variant-updated booster vaccination.