Persistent Immunity against SARS-CoV-2 in Individuals with Oncohematological Diseases Who Underwent Autologous or Allogeneic Stem Cell Transplantation after Vaccination

SIMPLE SUMMARY: Individuals with hematological diseases are particularly susceptible to COVID-19, and their vaccination has been a priority since the beginning of the pandemic. However, due to the disease itself or the treatment they receive, the protection achieved after vaccination may not be protected from severe forms of COVID-19. In this study, we analyzed the characteristics of the immune response developed by individuals with hematological cancer who received a stem cell transplant to overcome their disease after receiving the full vaccination schedule. All participants showed reduced levels of antibodies in plasma, but the cellular response of individuals with an autologous transplant was very similar to healthy donors, while it was severely impaired in individuals who received the transplant from other individuals (allogeneic). Interestingly, the transplant did not affect the immune response against SARS-CoV-2, and most infections reported after the transplant were mild, proving that some level of protection was preserved after the transplant. ABSTRACT: The high morbimortality due to SARS-CoV-2 infection in oncohematological diseases (OHD) and hematopoietic stem cell transplant (HSCT) recipients in the pre-vaccine era has made vaccination a priority in this group. After HSCT, the immune responses against common vaccines such as tetanus, varicella, rubella, and polio may be lost. However, the loss of immunity developed by COVID-19 vaccination after HSCT has not been completely defined. In this study, both humoral and cellular immunity against SARS-CoV-2 were analyzed in 29 individuals with OHD who were vaccinated before receiving allogeneic (n = 11) or autologous (n = 18) HSCT. All participants had low but protective levels of neutralizing IgGs against SARS-CoV-2 after HSCT despite B-cell lymphopenia and immaturity. Although antibody-dependent cellular cytotoxicity was impaired, direct cellular cytotoxicity was similar to healthy donors in participants with autologous-HSCT, in contrast to individuals with allogeneic–HSCT, which severely deteriorated. No significant changes were observed in the immune response before and after HSCT. During follow-up, all reported post-HSCT SARS-CoV-2 infections were mild. This data emphasizes that COVID-19 vaccination is effective, necessary, and safe for individuals with OHD and also supports the persistence of some degree of immune protection after HSCT, at least in the short term, when patients cannot yet be revaccinated.