An mRNA Vaccine against SARS-CoV-2 — Preliminary Report | NEJM [Moderna Vaccine Phase 1 Trial summary] https://www.nejm.org/doi/full/10.1056/NEJMoa2022483

The mRNA-1273 vaccine was immunogenic, inducing robust binding antibody responses to both full-length S-2P and receptor-binding domain in all participants after the first vaccination in a time- and dose-dependent fashion.

Commensurately high neutralizing antibody responses were also elicited in a dose-dependent fashion. Seroconversion was rapid for binding antibodies, occurring within 2 weeks after the first vaccination,

but pseudovirus neutralizing activity was low before the second vaccination, which supports the need for a two-dose vaccination schedule.

It is important to note that both binding and neutralizing antibody titers induced by the two-dose schedule were similar to those found in convalescent serum specimens.

In humans, phase 3 efficacy trials will allow assessment of the correlation of vaccine-induced immune responses with clinical protection.

A phase 2 trial of mRNA-1273 in 600 healthy adults, evaluating doses of 50 μg and 100 μg, is ongoing (ClinicalTrials number, NCT04405076. opens in new tab). A large phase 3 efficacy trial, expected to evaluate a 100-μg dose, is anticipated to begin during the summer of 2020.

This longitudinal assessment is relevant given that natural history studies suggest that SARS-CoV and MERS-CoV (Middle East respiratory syndrome coronavirus) infections, particularly mild illnesses, may not generate long-lived antibody responses

However, participants will be followed for 1 year after the second vaccination with scheduled blood collections throughout that period to characterize the humoral and cellular immunologic responses.

This is what Moderna Study indicates. Robust anti bodies response to in initial trials of Vaccine on neutralising the spike protien binding of SARS-CoV2 but a larger assessment needed as Anti Bodies in SARS Viruses peters out rather quickly compared to other viruses.