Enhanced SARS-CoV-2 IgG durability following COVID-19 mRNA booster vaccination and comparison of BNT162b2 with mRNA-1273.

ABSTRACT

BACKGROUND: BNT162b2 (Pfizer/BioNTech, Cominarty) and mRNA-1273 (Moderna, Spikevax) are mRNA vaccines that elicit antibodies against the SARS-CoV-2 spike receptor-binding domain (S-RBD) and have been approved by the Food and Drug Administration (FDA) to combat the COVID-19 pandemic. Because vaccine efficacy and antibody levels waned over time after the two-shot primary series, the FDA authorized a booster (third) dose for both mRNA vaccines to adults in the fall of 2021. OBJECTIVE: We sought to assess the magnitude and durability of S-RBD IgG after the booster mRNA vaccine dose in comparison to the primary series. We also compared S-RBD IgG levels after BNT162b2 and mRNA-1273 boosters and explored effects of age and prior infection. METHODS: Surrounding receipt of the second and third homologous mRNA vaccine doses, adults in an employee-based cohort provided serum and completed questionnaires, including information about prior COVID-19 infection. IgG to S-RBD was measured using an ImmunoCAP-based system. A subset of samples were assayed for IgG to SARS-CoV-2 nucleocapsid by commercial assay. RESULTS: 228 subjects had samples collected between 7 and 150 days after their primary series vaccine, and 117 subjects had samples collected in the same time frame after their boost. Antibody levels 7-31 days after the primary series and booster were similar, but S-RBD IgG was more durable over time after the boost, regardless of prior infection status. In addition, mRNA-1273 post-boost antibody levels exceeded BNT162b2 out to 5 months. CONCLUSION: COVID-19 mRNA vaccine boosters increase antibody durability, suggesting enhanced long-term clinical protection from SARS-CoV-2 infection compared to the two-shot regimen.