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Antibody Persistence through 6 Months after the Second Dose of mRNA-1273 Vaccine for Covid-19

Our take —

These results following up 33 participants of the Phase 1 trial for binding and neutralizing antibody titers 180 days following the second dose support the ongoing use of the mRNA-1273 vaccine (Moderna) due to the long-term durability of the antibody immune response that is elicited.

Study design


Study population and setting

This correspondence describes 6-month results of 33 healthy adult participants who are part of Moderna’s phase 1 trial of the mRNA-1273 vaccine. Binding and neutralizing antibody titers were measured on day 209, which is 180 days after the second dose of 100ug. Results were stratified by age (18-55 years, 56-70 years, and 71 years).

Summary of Main Findings

Binding antibody titers remained high in all age groups, with slightly decreasing mean titers as age group increased. Nearly all participants had neutralizing antibody activity in both the psuedovirus neutralization assays and the more sensitive live-virus focus-reduction neutralization mNeon Green test. Neutralizing antibody half-life was calculated to be between 173 – 202 days, depending on the assay used.

Study Strengths

These results are taken from participants who have been followed for six months, since the start of Moderna’s phase 1 vaccine trial. Also, ongoing studies are being conducted to gather data beyond 6 months, and also to determine effectiveness of boosters against emerging variants.


No true correlate of protection against SARS-CoV-2 has been established, so the antibody titers and assays that best correlate with vaccine efficiency are not known.

Value added

The first report of long-term durability of binding and neutralizing antibodies from participants in Moderna’s phase 1 trial of their mRNA-1273 vaccine.

This review was posted on: 19 April 2021