Humoral Response to the Third Dose of Sars-Cov-2 Vaccine in Kidney Transplant Recipients

Background. Most solid organ transplant recipients did not develop an appreciable serologic response after 2 doses of the mRNA SARS-CoV-2 vaccine.Methods. We analyzed the humoral response after a third dose of the BNT162b2 vaccine in 130 kidney transplant recipients, compared to 48 health care workers, and associated factors, including prevaccine cellular immune response, by evaluating intracellular cytokine production after stimulation of donor's peripheral blood mononuclear cells.Results. After 2 doses, most of the controls (47 out of 48, 98%) and only 40% of kidney recipi-ents (52 of 130) kidney recipients were seropositive (P < .001). Most seronegative recipients devel-oped a serologic response after the booster (47 out 78, 60%), thus bringing the total number of seropositive recipients to 99 out of 130 (76%). After the third dose, there was a significant increase in antibodies titers in both groups. Decreased humoral response was significantly associated with an older age, lower lymphocyte count, and a lower level of antibodies before booster administra-tion. CD4+TNFa+ and CD4+INFg+ were correlated with mean increase in antibody titers. Conclusions. A third dose of the BNT162b2 mRNA vaccine in kidney recipients is safe and effectively results in increased IgG anti-S levels, including in individuals who were seronegative after 2 doses. Long-term studies of the length of the immune response and protection are required.

Automated summary

Most solid organ transplant recipients did not have a significant serologic response after two doses of the mRNA SARS-CoV-2 vaccine. However, a third dose of the BNT162b2 vaccine resulted in an increased antibody titer in kidney transplant recipients, especially in those who were seronegative after the initial doses. Factors such as age, lymphocyte count, and antibody levels before booster administration were associated with a decreased humoral response.