COVID-19 vaccination in solid-organ transplant recipients: generating new data as fast as possible, but taking clinical decisions as slow as necessary

Serological Response and Clinical Protection of Anti-SARS-CoV-2 Vaccination and the Role of Immunosuppressive Drugs in a Cohort of Kidney Transplant Patients

Vaccination against SARS-CoV2 represents a key weapon to prevent COVID-19, but lower response rates to vaccination have frequently been reported in solid organ transplant recipients. The aim of our study was to evaluate the rate of seroconversion to SARS-CoV-2 mRNA vaccines in a cohort of kidney transplant recipients and the potential role of the different immunosuppressive regimens. We conducted an observational retrospective cohort study in kidney transplant patients vaccinated for COVID-19. For each patient, we evaluated IgG anti-S-RBD SARS-CoV-2 titers immediately before the administration of first COVID-19 vaccination dose, 20 days after the first dose and 40 days after the second dose. Moreover, we evaluated the type of immunosuppressive treatment and the incidence of vaccine breakthrough SARS-CoV-2 infection. We enrolled 121 kidney transplant patients vaccinated for COVID-19. At the time of administration of the first vaccine dose, all patients had a negative antibody titer; only 4.1% had positive antibody titers 20 days after the first dose. More than half patients 62 (51%) had protective antibody titers 40 days after the second dose. A total of 18 Solid Organ Transplant Recipients (SOTRs) (14.9%) got a SARS-CoV-2 breakthrough infection during the study period. With regard to immunosuppressive regimen, patients on mycophenolate-based regimen (48.7%) showed the lowest antibody response rates (27.5%) compared to other regimens. Our study confirms that kidney transplant patients show a poor response to two doses of COVID-19 vaccination. Moreover, in our study the use of mycophenolate is significantly associated with a non-response to COVID-19 m-RNA vaccines.

Differences in Antibody Responses Between an Inactivated SARS-CoV-2 Vaccine and the BNT162b2 mRNA Vaccine in Solid-Organ Transplant Recipients

OBJECTIVES

Vaccination against SARS-CoV-2 may reduce COVID-19 mortality and complications in solidorgan transplant recipients, and we evaluated the associated antibody responses and adverse effects in this high-risk population.

MATERIALS AND METHODS

This prospective observational study (April-June 2021) included 10 liver and 38 kidney transplant recipients who received 2 vaccine doses (Sinovac, n = 31; or BioNTech, n = 17) and 56 healthy adults (Sinovac), all of whom provided 3 blood samples (prevaccination, 4 weeks after first dose, and 4-6 weeks after second dose) for quantitative tests (Abbott Quant assay forimmunoglobulin G antibodies against SARS-CoV-2 spike protein). Type I error was α = .05 in all statistical analyses (SPSS, version 25).

RESULTS

We analyzed demographic data, antibody responses, and adverse events after 2 doses of SARSCoV-2 vaccine, comparedimmune responses from solidorgan transplant recipients (median age, 36.5 years) versus healthy patients (median age, 37.5 years), and observed significantly higher seropositivity in healthy versus transplant patients after Sinovac vaccination (100% vs 67.5%; P = .001). However, we observed no significant seropositive differences for Sinovac versus BioNTech second doses in transplantrecipients. Median SARS-CoV-2 immunoglobulin G level after second dose was significantly higher in BioNTech (1388.6 AU/mL) versus Sinovac patients (136.6 AU/mL) (P = .012). The seropositivity difference between the 2 vaccines was significant in participants 24 to 44 years old (P = .040). The rate of at least 1 side effect was 82.4% (n = 14) for BioNTech vaccine and 32.3% (n = 10) for Sinovac vaccine, and the difference was statistically significant.The most common side effect was arm pain (significantly higher in BioNTech group).

CONCLUSIONS

Solid-organ transplant recipients demonstrated inadequate vaccine responses (higher risk of complications and mortality) versus healthy patients. Furthermore, immune responses may differ between vaccines. Therefore, additional vaccine doses and strict control measures remain crucial.