Antibody response after third vaccination with mRNA-1273 or BNT162b2: Extension of a randomized controlled SARS-CoV-2 noninferiority vaccine trial in patients with different levels of Immunosuppression (COVERALL-2).  Open Forum Infectious Diseases
In this randomized trial, nested within the Swiss HIV Cohort (SHCS) and the Swiss Transplant Cohort Study (STCS), Griessbach et al. compared the antibody responses after receiving the third dose of one of the two mRNA vaccines against COVID-19 (Moderna mRNA-1273 vs. Pfizer-BioNTech BNT162b2) in people with HIV (PWH) or solid organ transplant (SOT) recipients.
The study extends the previous comparison of immune response after receiving two mRNA vaccine doses (COVERALL-1). Between December 2021 and March 2022, cohort participants who were previously randomized in COVERALL-1 and received a third mRNA vaccine dose were included in the study. The primary outcome was the proportion of individuals with a positive antibody response 8 weeks after the third dose, defined as SARS-CoV-2 spike S1 antibody titer of ≥100 units/mL (Elecsys S). The prespecified non-inferiority margin was -10%.
Of the 430 individuals randomized in COVERALL-1, 312 (72.6%) were included in the present study. The median age was 54 years (IQR 44-60), 25% were women, 90.7% were PWH, and 9.3% were SOT recipients. Of PWH, 84% had CD4 cell counts >350 cells/µL, and 95% had an undetectable HIV viral load. Eight weeks after receiving the third dose of Moderna mRNA-1273, 95.3% (95% CI 91.9–98.7) had a positive vaccine response, compared to 98.1% (95.9–100) who received Pfizer-BioNTech BNT162b (difference -2.8 percentage points, 95% CI -6.8 to 1.3). Whereas 276 of the 277 PWH (99.6%, 95% CI 98.9–100.9) showed an adequate immune response, this was the case in only 17 of the 26 SOT recipients (65.4%, 47.1–83.7).
In conclusion, the study showed that the antibody response after a third dose of Moderna mRNA-1273 was non-inferior to a third dose of Pfizer-BioNTech BNT162b2 among PWH and SOT recipients.