Differences in Antibody Responses Between an Inactivated SARS-CoV-2 Vaccine and the BNT162b2 mRNA Vaccine in Solid-Organ Transplant Recipients

Objectives: Vaccination against SARS-CoV-2 may reduce COVID-19 mortality and complications in solidorgan transplant recipients, and we evaluated the associated antibody responses and adverse effects in this high-risk population. Materials and Methods: This prospective observational study (April-June 2021) included 10 liver and 38 kidney transplant recipients who received 2 vaccine doses (Sinovac, n = 31; or BioNTech, n = 17) and 56 healthy adults (Sinovac), all of whom provided 3 blood samples (prevaccination, 4 weeks after first dose, and 4-6 weeks after second dose) for quantitative tests (Abbott Quant assay for immunoglobulin G antibodies against SARS-CoV-2 spike protein). Type I error was alpha = .05 in all statistical analyses (SPSS, version 25). Results: We analyzed demographic data, antibody responses, and adverse events after 2 doses of SARS-CoV-2 vaccine, compared immune responses from solidorgan transplant recipients (median age, 36.5 years) versus healthy patients (median age, 37.5 years), and observed significantly higher seropositivity in healthy versus transplant patients after Sinovac vaccination (100% vs 67.5%; P = .001). However, we observed no significant seropositive differences for Sinovac versus BioNTech second doses in transplant recipients. Median SARS-CoV-2 immunoglobulin G level after second dose was significantly higher in BioNTech (1388.6 AU/mL) versus Sinovac patients (136.6 AU/mL) (P = .012). The seropositivity difference between the 2 vaccines was significant in participants 24 to 44 years old (P = .040). The rate of at least 1 side effect was 82.4% (n = 14) for BioNTech vaccine and 32.3% (n = 10) for Sinovac vaccine, and the difference was statistically significant. The most common side effect was arm pain (significantly higher in BioNTech group). Conclusions: Solid-organ transplant recipients demonstrated inadequate vaccine responses (higher risk of complications and mortality) versus healthy patients. Furthermore, immune responses may differ between vaccines. Therefore, additional vaccine doses and strict control measures remain crucial.