(652) Effect of Seroconversion after SARS-CoV-2 Vaccination on the Severity of COVID-19 Disease in Heart Transplant Recipients

PURPOSE: Heart transplant (HTX) recipients are prone to develop serious symptoms after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and their vaccination is often ineffective. In this high-volume single center study, we aimed to examine the seroconversion rates achieved with various types and doses of SARS-CoV-2 vaccines and assessed factors influencing vaccine immunogenicity and predictors of severe SARS-CoV-2 infection. METHODS: 229 HTX recipients were enrolled at a university clinic. Type of the first two doses of vaccine included mRNA, vector and inactivated vaccines as well. We carried out analyses on seroconversion after the second and third doses of vaccination and on severity of coronavirus disease 2019 (COVID-19). Anti-SARS-CoV-2 IgG levels were measured with Elecsys immunoassay (Roche). Effect of the first two vaccine doses was studied on patients who did not suffer SARS-CoV-2 infection before antibody measurement (n=175). Seroconversion after the third vaccine was analysed among seronegative patients after two doses (n=53). Predictors for severe infection defined as pneumonia, hospitalization or death was assessed in all HTX recipients who had COVID-19 (n=92). Logistic regression was applied for further analyses. RESULTS: 62% of the recipients became seropositive after the second vaccination. Longer time between HTX and vaccination (OR: 2.35, 95% CI: 1.28 - 4.49, p=0.007) and mRNA type of vaccine (OR: 4.83, 95% CI: 1.33 - 17.5, p=0.012) were predictors of seroconversion. 58% of the non-responsive patients became seropositive after receiving the third vaccine. Male sex increased the chance of IgG production after the third dose (OR: 5.65, 95% CI: 1.61 - 22.7, p=0.009). Clinical course of SARS-CoV-2 infection was severe in 32%. Of all parameters assessed, only seropositivity was proven to have a protective effect against severe infection (OR: 0.12, 95% CI: 0.02 - 0.64, p=0.019). CONCLUSION: Longer time since HTX, mRNA vaccine type and male sex promoted seroconversion after SARS-CoV-2 vaccination in HTX recipients. Seropositivity was proven to be protective against severe SARS-CoV-2 infection in single center cohort. Routine screening of HTX patients for anti-SARS-COV-2 antibodies may help to identify patients at risk for severe infection requiring addtional measures of anti-SARS-CoV-2 protection.