Patients receiving CD19 CAR T-cell therapy for relapsed/refractory lymphoma experience prolonged and profound B-cell aplasia and hypogammaglobulinemia, placing them at a higher risk for severe COVID-19. Independently, Oh et al and Atanackovic et al demonstrate that despite attenuated humoral response to mRNA-based vaccines, patients demonstrate normal or heightened functional T-cell responses, including antiviral T-cell activity against SARS-CoV-2 variants including Omicron. Collectively, these data reinforce the importance of COVID-19 vaccination following CD19 CAR T-cell therapy, despite long-term B-cell aplasia.

Objectives Solid organ transplant recipients (SOTR) receiving post‐transplant immunosuppression show increased COVID‐19‐related mortality. It is unclear whether an additional dose of COVID‐19 vaccines can overcome the reduced immune responsiveness against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) variants. Methods We analysed humoral immune responses against SARS‐CoV‐2 and its variants in 53 SOTR receiving SARS‐CoV‐2 vaccination. Results Following the initial vaccination series, 60.3% of SOTR showed no measurable neutralisation and only 18.9% demonstrated neutralising activity of > 90%. More intensive immunosuppression, antimetabolites in particular, negatively impacted antiviral immunity. While absolute IgG levels were lower in SOTR than controls, antibody titres against microbial recall antigens were higher. By contrast, SOTR showed reduced vaccine‐induced IgG/IgA antibody titres against SARS‐CoV‐2 and its delta variants and fewer linear B‐cell epitopes, indicating reduced B‐cell diversity. Importantly, a third vaccine dose led to an increase in anti‐SARS‐CoV‐2 antibody titres and neutralising activity across alpha, beta and delta variants and to the induction of anti‐SARS‐CoV‐2 CD4 + T cells in a subgroup of patients analysed. By contrast, we observed significantly lower antibody titres after the third dose with the omicron variant compared to the ancestral SARS‐CoV‐2 and the improvement in neutralising activity was much less pronounced than for all the other variants. Conclusion Only a small subgroup of solid organ transplant recipients is able to generate functional antibodies after an initial vaccine series; however, an additional vaccine dose resulted in dramatically improved antibody responses against all SARS‐CoV‐2 variants except omicron where antibody responses and neutralising activity remained suboptimal.

Anti-SARS-CoV-2 antibodies are crucial for protection from future COVID-19 infections, limiting disease severity, and control of viral transmission. While patients with the most common type of hematologic malignancy, B cell lymphoma, often develop insufficient antibody responses to messenger RNA (mRNA) vaccines, vaccine-induced T cells would have the potential to ‘rescue’ protective immunity in patients with B cell lymphoma. Here we report the case of a patient with B cell lymphoma with profound B cell depletion after initial chemoimmunotherapy who received a total of six doses of a COVID-19 mRNA vaccine. The patient developed vaccine-induced anti-SARS-CoV-2 antibodies only after the fifth and sixth doses of the vaccine once his B cells had started to recover. Remarkably, even in the context of severe treatment-induced suppression of the humoral immune system, the patient was able to mount virus-specific CD4+ and CD8+ responses that were much stronger than what would be expected in healthy subjects after two to three doses of a COVID-19 mRNA vaccine and which were even able to target the Omicron ‘immune escape’ variant of the SARS-CoV-2 virus. These findings not only have important implications for anti-COVID-19 vaccination strategies but also for future antitumor vaccines in patients with cancer with profound treatment-induced immunosuppression.

BACKGROUND: Solid organ transplant recipients (SOTR), who typically receive post-transplant immunosuppression, show increased COVID-19-related mortality. It is unclear whether an additional dose of COVID-19 vaccines in SOTR can overcome the reduced immune responsiveness against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants. METHODS: We performed a prospective cohort study of 53 SOTR receiving SARS-CoV-2 vaccination into a prospective cohort study performing detailed immunoprofiling of humoral immune responses against SARS-CoV-2 and its variants. RESULTS: Prior to the additional vaccine dose, 60.3% of SOTR showed no measurable neutralization and only 18.9% demonstrated neutralizing activity of >90% following two vaccine doses. More intensive immunosuppression, antimetabolites in particular, negatively impacted antiviral immunity. While absolute IgG levels were lower in SOTR than controls, antibody titers against microbial recall antigens were in fact higher. In contrast, SOTR showed reduced vaccine-induced IgG/IgA antibody titers against SARS-CoV-2 and its delta variants. Vaccinated SOTR showed a markedly fewer linear B cell epitopes, indicating reduced B cell diversity. Importantly, a third vaccine dose led to an increase in anti-SARS-CoV-2 antibody titers and neutralizing activity across alpha, beta and delta variants. However, we observed a significant decrease in anti-spike antibody titers with the omicron variant. CONCLUSIONS: Only a small subgroup of SOTR generated functionally relevant antibodies after completing the initial vaccine series based on dysfunctional priming of immune responses against novel antigens. An additional dose of the vaccine results in dramatically improved antibody responses against all SARS-CoV-2 variants except omicron.