Immune response and protection over 12 months after a fourth dose of two types of COVID-19 vaccines in Australia

The bivalent mRNA vaccine from Moderna demonstrated higher IgG levels against the Ancestral strain compared to the Novavax protein vaccine at six and 12 months post-vaccination.

• IgG levels against the Ancestral strain were significantly higher in the Moderna group at both six months (GMR: 1.59) and 12 months (GMR: 1.34) compared to the Novavax group.
• For Omicron variants BA.1, BA.4/5, and JN.1, IgG levels in the Moderna group were also higher than in the Novavax group at both time points, with GMRs ranging from 1.62 to 1.66 at six months and 1.33 to 1.43 at twelve months.
• No differences in T cell immunity, as measured by IFN-γ concentrations, were found between the two vaccine groups.
• Both vaccine groups had higher IgG levels against the Ancestral strain and Omicron variants compared to a control group at six months (GMR: 1.24 to 2.40) and twelve months (GMR: 1.04 to 1.62).
• The control group had a higher SARS-CoV-2 infection rate (68.1%) over the 12-month period compared to the Moderna (43.0%) and Novavax (47.0%) groups.

Simplified