Vaccine Immunogenicity to SARS-CoV-2 in Renal Transplant Patients Under Three Different Immunosuppressive Regimens: Evaluation of Antibody Titers.

BACKGROUND

In kidney transplant recipients (KTRs), the immunogenic response to vaccines is considered to be low in achieving a robust immune response.

METHODS

This study evaluated the serological response of KTRs who received previous immunization with the anti-SARS-CoV-2 vaccine ChAdOx1 and 2 booster doses of BNT162b2 vaccine. Patients were on 3 different immunosuppressive regimens: azathioprine (AZA), mycophenolic acid precursors (MPA), or mammalian target of rapamycin inhibitors (mTORi). All were also on tacrolimus and prednisone. Healthy volunteers served as controls. Blood samples were collected before receiving the first booster dose, 4 to 6 weeks after the first booster dose, and 6 months after the second booster dose.

RESULTS

Before the vaccine booster, the MPA group had a tendency, but not statistically significant, of a lower reactivity rate than the AZA, mTORi, and control groups. The percentage of reactivity was AZA 54%, MPA 42%, mTORi 55%, and controls 73%, respectively. After the first booster, the serological response had a significant increase, indicating the effectiveness of the heterologous vaccine dose in all groups (P < .05 in percentage of responders in serological titers), which reached the following percentage of seroreactivity: AZA 90%, MPA 80%, mTORi 88%, and controls 100%, respectively. After the second booster dose, seroreactivity was 81%, 91%, and 100%, respectively.

CONCLUSIONS

After the vaccine booster, there was no statistically significant difference in IgG titers among the AZA, MPA, and mTORi groups in KTRs that demonstrated that the additional booster regimen with BNT162b2 increased the initial low responsiveness, increasing seroconversion rates.