BACKGROUND The repeated waves of the COVID-19 pandemic have highlighted the necessity to optimize vaccine responses in immunocompromised populations. We investigated the safety and immunogenicity of a third, booster, dose of the Pfizer BNT162b2 vaccine in heart transplant (HT) patients. METHODS The cohort comprised 96 adult HT patients who received a third homologous dose of the BNT162b2 vaccine 168 days after the second dose. The vaccine-induced antibody responses of both receptor-binding domain (RBD) IgG and neutralizing antibodies were assessed in all patients, with a positive antibody response being defined as the presence of either IgG anti-RBD or neutralizing antibodies. For a subset of patients, T cell response was also studied. RESULTS The third dose was associated with a low rate of adverse events, mostly mild pain at the injection site. No serious adverse events were recorded, and there were no episodes of rejection. At 18 days following the third dose of the vaccine, the positive antibody response increased from 23% to 67%, with a corresponding increase in neutralizing capacity. The third dose elicited SARS-CoV-2 neutralization titers >9-fold and IgG anti-RBD antibodies >3-fold of the range achieved after the two primary doses. Mycophenolate use, lower eGFR and higher C-reactive protein were independently associated with a reduced likelihood of generating an immune response. Importantly, a specific T-cell response following the third dose was evident in the majority of transplant recipients. CONCLUSIONS An homologous third booster dose of the BNT162b2 vaccine gave overall consistent tolerability and a good safety profile, while eliciting humoral and cellular immune responses.

Objectives The immunogenicity and safety of the Pfizer-BioNTech BNT162b2 mRNA vaccine in people living with HIV-1 (PLWH) are unknown. We thus aimed to assess the immunogenicity and safety of this vaccine in PLWH. Methods In this prospective open study, we enrolled 143 PLWH, aged ≥18 years, who attended our clinic and 261 immunocompetent health care workers (HCWs). SARS-CoV-2 receptor binding domain (RBD) IgG and neutralizing antibodies were measured. Adverse events, viral load and CD4 cell counts were monitored. Results At a median of 18 days (IQR 14-21) after the second dose, anti-RBD IgG was positive in 139/141 (98%) PLWH. Among HCWs, 258/261 (98.9%) developed anti-RBD IgG at a median of 26 (IQR 24-27) days after the second dose. Following the second dose, immune sera neutralized SARS-CoV-2 pseudo-virus in 97% and 98% of PLWH and HCW, respectively. Adverse events were reported in 60% of PLWH, mainly pain at the injection site, fatigue, and headache. AIDS-related adverse events were not reported. HIV viral load increased in 3/143 (2%) patients from < 40 copies/mL to ≤ 100 copies/mL. CD4+ T cell count decreased from a geometric mean of 700 (95% CI 648–757) cells per μL to 633.8 (95% CI 588–683) cells per μL (P<0.01). Conclusions BNT162b2 mRNA vaccine appears immunogenic and safe in PLWH who are on ART with unsuppressed CD4 count and suppressed viral load.

Data on the safety and efficacy of SARS-CoV-2 vaccines in immunocompromised populations are sparse. We conducted a prospective study of 77 heart transplant (HT) recipients vaccinated with two doses of BNT162b2 vaccine and monitored for adverse events following both doses, the receptor-binding domain (RBD) IgG response, and neutralizing antibodies. BNT162b2 vaccination was associated with a low rate of adverse events, characterized mostly by pain at the injection site. By a mean 41 days post second dose there were no clinical episodes of rejection, as suggested by a troponin leak or allograft dysfunction. At a mean 21 days following the second dose, IgG anti-RBD antibodies were detectable in 14 (18%) HT recipients. Immune sera neutralized SARS-CoV-2 pseudo-virus in 8 (57%) of those with IgG anti-RBD antibodies. Immunosuppressive regimen containing mycophenolic acid was associated with lower odds of an antibody response (OR=0.12, P=0.042). Whether a longer time-frame for observation of an antibody response is required after vaccination in immunosuppressed individuals remains unknown.