The Predictors of COVID-19 Immunogenicity Elicited by Vaccines Against SARS-CoV-2 in Stem Cell Transplant Recipients

Introduction: The literature falls short in providing thorough investigations into the influence of COVID-19 vaccination among those undergoing hematopoietic stem cell transplantation (HSCT). Materials and Methods: This prospective study evaluates COVID-19 antibody levels in HSCT recipients. The HSCT patients, having undergone transplantation at least three months prior, received BNT162b2 mRNA, Gam-COVID-Vac adenoviral, or BBIBP-CorV inactivated vaccines. Blood samples were taken 2-24 weeks post second dose. Results: The study involved 28 participants, comprising nine allogeneic-HSCT and 19 autologous-HSCT recipients. Among them, 18 (64.2%) exhibited positive results in SARS-CoV-2 neutralizing antibody tests, occurring at a median of 10.5 weeks (ranging from 2 to 24 weeks). In multivariate logistic regression analysis, age and a higher Charlson Comorbidity Index emerged as statistically significant variables linked with suboptimal antibody responses. Interestingly, no significant disparities surfaced in terms of anti-SARSCoV-2 spike, SARS-CoV-2 (IgG + neutralizing) antibodies, and SARS-CoV-2 (neutralizing) antibodies titers across various vaccine types and transplantation modes. However, the anti-SARS-CoV-2 nucleocapsid titers demonstrated a significant increase in patients who received the BBIBP-CorV inactivated vaccine (Sinopharm, China). Moreover, within the non -vaccinated BMT subgroup, a slightly higher yet insignificant incidence of COVID-19 was observed in comparison to the vaccinated subgroup (2/28-7.1% vs. 3/11-27.2%, p= 0.125). During the six-month post -vaccination follow-up, COVID-19 incidence was 144.9 per 1000 patient -years in the vaccinated group, contrasting with 545.4 per 1000 patient -years in the unvaccinated group. Hence, a substantial vaccination efficacy of 73.4% was noted. No fatalities were reported among either vaccinated or unvaccinated HSCT patients who contracted COVID-19 during the 30 -day follow-up period. Conclusion: The inactivated vaccine demonstrated antibody responses comparable to the Pfizer-BioNTech vaccine.