Comparative 6-Month Wild-Type and Delta-Variant Antibody Levels and Surrogate Neutralization for Adults Vaccinated...

While mRNA vaccines are highly efficacious against short-term COVID-19, long-term immunogenicity is less clear. We compared humoral immunogenicity between BNT162b2 and mRNA-1273 vaccines 6 months after the first vaccine dose, examining the wild-type strain and multiple Delta-variant lineages. Using samples from a prospective observational cohort study of adult paramedics, we included COVID-19-negative participants who received two BNT162b2 or mRNA-1273 vaccines, and provided a blood sample 170 to 190 days post first vaccine dose. We compared wild-type spike IgG concentrations using the Mann-Whitney U test. We also compared secondary outcomes of: receptor binding domain (RBD) wild-type antibody concentrations, and inhibition of angiotensin-converting enzyme 2 (ACE-2) binding to spike proteins from the wild-type strain and five Delta-variant lineages. We included 571 adults: 475 BNT162b2 (83%) and 96 mRNA-1273 (17%) vaccinees, with a mean age of 39 (SD = 10) and 43 (SD = 10) years, respectively. Spike IgG antibody concentrations were significantly higher (P < 0.0001) for those who received mRNA-1273 (GM 601 BAU/mL [GSD 2.05]) versus BNT162b2 (GM 375 BAU/mL [GSD 2.33) vaccines. Results of RBD antibody comparisons (P < 0.0001), and inhibition of ACE-2 binding to the wild-type strain and all tested Delta lineages (all P < 0.0001), were consistent. Adults who received two doses of mRNA-1273 vaccines demonstrated improved wild-type and Delta variant-specific humoral immunity outcomes at 6 months compared with those who received two doses of the BNT162b2 vaccine. IMPORTANCE The BNT162b2 and mRNA-1273 mRNA SARS-CoV-2 vaccines have demonstrated high efficacy for preventing short-term COVID-19. However, comparative long-term effectiveness is unclear, especially pertaining to the Delta variant. We tested virus-specific antibody responses 6 months after the first vaccine dose and compared individuals who received the BNT162b2 and mRNA-1273 SARS-CoV-2 vaccines. We found that individuals who received the mRNA-1273 vaccine demonstrated superior serological markers at 6 months in comparison with those who received the BNT162b2 vaccine.