Serologic response to a third dose of an mRNA-based SARS-CoV-2 vaccine in lung transplant recipients

Lung transplant recipients have an increased risk for severe coronavirus disease 2019 (COVID-19) due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A third dose of a SARS-CoV-2 vaccine has been recommended for all solid organ transplant recipients, but data from lung transplant recipients specifically are scarce. In this study, the serologic response to a third dose of an mRNA-based SARS-CoV-2 vaccine was measured in 78 lung transplant recipients. Sixty-two percent (n = 48) had a serological response to vaccination, which was significantly higher than after the second vaccine dose (27 patients (35%); p = 0.0013). A positive serologic response was associated with having had COVID-19 (p = 0.01), and higher serum IgG level and complement mannose binding lectin pathway activity prior to vaccination (p = 0.04 and p = 0.03, respectively). Serologic response was not associated with the dose of mycophenolate mofetil or prednisone or other immune status parameters. Eleven patients (14%) developed COVID-19 after the second or third vaccine dose, but this did not associate with serologic response after the second vaccine dose (9% in patients who developed COVID-19 versus 39% in patients who did not develop COVID-19 (p = 0.09)), or with serologic response above cut-off values associated with clinical protection in previous studies. In conclusion, the response to mRNA-based SARS-CoV-2 vaccines in lung transplant recipients improves significantly after a third vaccine dose. Factors associated with a positive serologic response are having had COVID-19 prior to vaccination, and serum IgG and complement mannose binding lectin pathway activity prior to vaccination. Serologic response did not associate with clinical protection against COVID-19 in this study.