Immunogenicity of Two Doses of ChAdOx1 nCoV-19 Vaccine in Lung Transplant Recipients

PURPOSE: Lung transplant recipients (LTR) are at higher risk to develop severe SARS-CoV2 pneumonia, due to the immunosuppressive regimen, which further hampers their immune response to vaccination. Indeed, is has been shown that LTR mount weak antibody response after SARS-CoV2 mRNA vaccination. Nevertheless, the immunogenicity of ChAdOx1 nCoV-19 vaccine has not yet been studied in LTR. METHODS: 49 lung-transplant SARS-CoV2 seronegative recipients were enrolled in a prospective cohort study and received the two doses regimen, day 0 and day 90, of the ChAdOx1 nCoV-19 vaccine. Immune response was assessed by measuring total anti-SARS-CoV2 antibodies (Anti-SARS-CoV2 total Ig immunoassay, Ortho Clinical Diagnostics, USA) at D0, D24, D84, D112 and D180. ENDPOINTS: At D180, 25% of LTR had positive total antibody levels (positivity threshold, > 1 (sample signal/threshold value). Age, CMV status, gender and initial respiratory disease had no influence on the immune response. Immune response was improved in patients whose immunosuppressive regimen did not include mycophenolate mofetil (53% versus 0%, p < 0.0001), and in patients who were transplanted for more than 18 months (0% versus 41%, p < 0.05), probably due to more aggressive immunosuppressive regimen in recently transplanted patients. CONCLUSIONS: Immunogenicity of ChAdOx1 nCoV-19 vaccine is poor in LTR, with only one in four patients mounting significant anti-SARS-CoV2 immune response at D180. Of note, according to expert recommendations, most LTR received an heterologous booster dose with a SARS-CoV2 mRNA vaccine (BNT162b2). Additional serological analyses are planned to decipher whether vaccinal response is improved after the third dose in LTR. Results will be updated accordingly and presented at the 42(nd) ISHLT Congress.