Immune Response to SARS-CoV-2 Vaccine among Heart Transplant Recipients: A Systematic Review

Abstract

Background Heart transplant (HTX) recipients are at a significantly higher risk of adverse clinical outcomes, due to chronic immunosuppression and co-existence of other chronic conditions, when contracting the SARS-CoV-2 infection. Although vaccination against SARS-CoV-2 is currently the most promising measure for the prevention of severe Coronavirus Disease 2019 (COVID-19) among solid organ transplant recipients, the extent of immune response and its protective efficacy among patients receiving HTX has not been sufficiently studied. Methods We performed a systematic review of the literature by inquiring PubMed/Medline to identify original studies among HTX recipients, who had received at least one dose of the SARS-CoV-2 vaccine. Data on the measured humoral or cellular immune response was collected from all the eligible studies. Factors associated with a poor immune response were further investigated within these studies. Results A total of 12 studies comprising 563 HTX recipients were included. The average age of the study participants was 60.8 years. Sixty four percent of the study population were male. Ninety percent of the patients had received an mRNA vaccine (Pfizer/ BNT162b2 or Moderna/mRNA-1273). A positive immune response to SARS-CoV-2 vaccine was variably reported in 0% to 100% of the patients. Older age (> 65 years), vaccine dose (first, second, or third), time since HTX to the first dose of the vaccine, the time interval between the latest dose of the vaccine and measurement of the immune response, and the type of immunosuppressive regimen were all indicated as potential determinants of a robust immune response to the SARS-CoV-2 vaccination. Conclusion HTX recipients demonstrate a weaker immune response to the vaccination against SARS-CoV-2 compared to the general population. Older age, anti-metabolite agents such as mycophenolate mofetil, and vaccination during the first year following the HTX have been indicated as potential determinants of a poor immune response.

Seroconversion after SARS‐CoV‐2 vaccination is protective against severe COVID‐19 disease in heart transplant recipients

“…Based on the literature, the percentage of HTX recipients achieving humoral immune response after two doses of SARS‐CoV‐2 vaccination ranges between 12% and 75% due to the high heterogeneity of the examined populations 10–13,23,24 . In our study, 62% of the HTX recipients became seropositive after two doses of the SARS‐CoV‐2 vaccine and 58% of the seronegative patients achieved seroconversion after a third, booster vaccination.…”

“…[26][27][28] For those solid organ transplant recipients who do not have sufficient antibody titers after three vaccines, the ESOT suggests the administration of additional booster vaccine doses or the consideration of pre-exposure prophylaxis with monoclonal antibodies. 14 In vaccinated HTX recipients, the weaker immune response was related to older age, 10,23,28 male sex, 23 vaccination within the first 23 or second 28 year after HTX and MMF or MPA immunosuppressant therapy. 10,12,23,28 Studies of solid organ transplant recipients showed that predictive factors for humoral response after vaccination were male sex, a longer period between transplantation and vaccination, living donor status, and liver transplantation.…”

“…14 In vaccinated HTX recipients, the weaker immune response was related to older age, 10,23,28 male sex, 23 vaccination within the first 23 or second 28 year after HTX and MMF or MPA immunosuppressant therapy. 10,12,23,28 Studies of solid organ transplant recipients showed that predictive factors for humoral response after vaccination were male sex, a longer period between transplantation and vaccination, living donor status, and liver transplantation. In contrast, older patients, recipients of a deceased donor organ, thoracic organ recipients, and those who received steroids or MMF/MPA-based immunosuppressive regimen were less likely to develop anti-SARS-CoV-2 F I G U R E 3 Proportion of vaccine types and the rate of seroconversion after the second vaccination in each group.…”

“…In vaccinated HTX recipients, the weaker immune response was related to older age, 10,23,28 male sex, 23 vaccination within the first 23 or second 28 year after HTX and MMF or MPA immunosuppressant therapy 10,12,23,28 . Studies of solid organ transplant recipients showed that predictive factors for humoral response after vaccination were male sex, a longer period between transplantation and vaccination, living donor status, and liver transplantation.…”

Severity of SARS-CoV-2 Omicron variant infection in heart transplant recipients

“…This differs from the results of several national cohort studies reporting a lower risk of severe outcomes following Omicron infection compared with Delta variant 3 , 4 . This discrepancy could be explained by the lower antibody response following vaccination associated with a waning over time of vaccine-induced immunity in HT recipients 8 , 9 . Indeed, only 24% of the patients from our cohort displayed antibody titers above the threshold of 260 BAU/mL at the time of COVID-19 diagnosis.…”