Most adult kidney transplant recipients (KTRs) exhibit a weak antibody response to the first injection of the Moderna mRNA COVID-19 vaccine, according to the findings of a prospective study published in Kidney International.1

“We already know that kidney transplant recipients tend to respond less well to vaccines because of the immunosuppression, but data concerning the anti-SARS-CoV-2 antibody response after COVID-19 vaccine in this population were lacking,” said first author Ilies Benotmane, MD, of Strasbourg University Hospital and the Fédération de Médecine Translationnelle (FMTS) in Strasbourg, France.

COVID-19 vaccine distribution programs worldwide have given priority to immunocompromised patients, including KTRs. Vaccination was recommended, however, for this patient population even though KTRs were not included in the vaccine clinical trials. Dr Benotmane and colleagues conducted a preliminary study investigating the efficacy and safety of the Moderna mRNA-1273 vaccine in KTRs by looking at the anti SARS CoV-2 antibody response after the first injection.

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The investigators studied 242 participants who received the first dose of the vaccine (100 µg) at a single site between January 21 and January 28, 2021. At baseline, all participants had a negative history for COVID-19 and tested negative for antibodies against the spike protein of SARS-CoV-2, the novel coronavirus that causes COVID-19. Only 26 KTRs (10.8%) had a positive antibody test result at 28 days post-injection, the investigators reported. The median IgG titer was 224 AU/mL in this group compared with less than 6.8 AU/mL in the seronegative group. Participants who seroconverted had a longer time from transplantation, received less immunosuppression, and had better kidney function compared with those who did seroconvert, according to the investigators. Mildly symptomatic COVID-19 developed in 1 patient 7 days after injection.

“We found that kidney transplant recipients have a weak anti-SARS-CoV-2 antibody response, ultimately resulting in a low seroconversion rate. Only 10.8% harbored antibodies after the first injection,” Dr Benotmane said. “The surprising thing is the huge difference with immunocompetent patients. In the preliminary studies of the mRNA vaccine, all patients harbored antibodies after the first dose.”

Clinicians may need to know that “the burden of immunosuppression may induce a weak anti-SARS-CoV-2 antibody response in KTRs after the first injection of an mRNA COVID-19 vaccine,” the authors concluded. They recommended close surveillance after vaccination in this patient population and suggested the possibility that a third dose may be required in less responsive patients.

“The burden of immunosuppression is very important as we can see the differences between the responders and non-responders in our study,” Dr Benotmane said. “It is important to continue the vaccination in KTRs and there is a need not to delay the second vaccine. Patients should also be careful to continue the protective measures against COVID-19.”

Findings Consistent With Prior Study

The findings from the current study are in line with those of a study published recently in JAMA.2 Of 436 solid organ transplant recipients who received the first dose of an mRNA SARS-CoV-2 vaccine, only 76 (17%) had detectable antispike antibodies after a median of 20 days, Brian Boyarsky, MD PhD, of Johns Hopkins University School of Medicine in Baltimore, Maryland, and colleagues reported. Although the majority of participants did not mount appreciable antibody responses, younger participants, participants not receiving anti-metabolite maintenance immunosuppression, and those who received the Moderna vaccine were more likely to develop antibody responses.

“The underlying implication is that transplant recipients and others on immunosuppressive agents should not assume immunity after vaccination,” Dr Boyarsky said in an interview. Strategies to improve the immune response to vaccination in transplant recipients need to be studied in a robust fashion, Dr. Boyarsky said.

Antibody Response May Just Take Longer

Rodger MacArthur, MD, an infectious disease specialist at the Medical College of Georgia in Augusta, agrees and said while the latest findings are intriguing, they must be viewed as preliminary. “It may just take [KTRs] longer or it may just take a second dose for them to develop antibodies,” Dr MacArthur said. “We really don’t know the clinical implications of this, and [the investigators] didn’t look at other influences. They didn’t look at the cellular responses like the killer lymphocyte responses.”

Studies have shown that in the realm of HIV infection, those individuals do not show a robust response to hepatitis B inoculations, he noted. The situation may be similar with KTRs. “We don’t know if they need a double dose,” he said. “There are a number of other ways they may be protected. It may be just a small amount of antibody is enough to protect against severe disease.”

Nephrologists should encourage all their KTRs to get vaccinated, Dr MacArthur said. Monitoring them for antibodies also may be appropriate. “It is still working in some percentage and we don’t know what might happen at 6 weeks after vaccination or later.”                                                          


  1. Benotmane I, Gautier -Vargas G, Cognard N, et al. Weak anti-SARS-CoV-2 antibody response after the first injection of an mRNA COVID-19 vaccine in kidney transplant recipients. Published online March 25, 2021. Kidney Int. doi:10.1016/j.kint.2021.03.014
  2. Boyarsky BJ, Werbel WA, Avery RK, et al. Immunogenicity of a single dose of SARS-CoV-2 messenger RNA vaccine in solid organ transplant recipients. Published online March 15, 2021. JAMA. doi:10.1001/jama.2021.4385