Antibodies are an important part of the body's defense against infection. Individuals who have no antibodies or very low antibody levels are considered less well protected from Coronavirus Disease 2019 (COVID-19) than those who have higher antibody levels. What level of antibodies is necessary for protection is currently unknown.

Inadequate antibody response to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccination has been described among kidney transplant recipients. The aim of this study is to elicit an antibody response to vaccination against SARS-CoV-2 in kidney transplant recipients who have failed to respond to two doses of either the Moderna COVID-19 vaccine or Pfizer-BioNTech Coronavirus Disease 2019 (COVID-19) vaccine.

This is an open label, non-randomized study in kidney transplant recipients who received two doses of either mRNA COVID-19 vaccine and have a negative (<0.8 U/mL) or low (titer <50 U/mL) SARS-CoV-2 antibody response using the Roche Elecsys® anti-RBD assay. Eligible participants will receive a third dose of the same mRNA vaccine as the prior two doses.

Inclusion Criteria:

Individuals who meet all the following criteria are eligible for enrollment as study participants-

1. Able to understand and provide informed consent;
2. Recipient of kidney transplant ≥12 months prior to enrollment, without treated allograft rejection in the 6 months preceding enrollment;
3. Received 2 doses of either the Moderna COVID-19 vaccine or Pfizer-BioNTech COVID-19 vaccine as specified in the respective Food and Drug Administration Emergency Use Authorization (FDA EUAs), >30 days and <8 months prior to enrollment ; and,
4. Negative (antibody titer < 0.8U/mL) or low (antibodies detected at titer ≤ 50 U/mL) response to the vaccine at > 30 days from dose 2 of the Moderna COVID-19 vaccine or the Pfizer BioNTech vaccine, using the Roche Elecsys® anti-Receptor Binding Domain (RBD) assay.

Exclusion Criteria:

Individuals who meet any of these criteria are not eligible for enrollment as study participants-

1. Recipient of any number of doses of any COVID vaccine product other than the Moderna COVID-19 vaccine or the Pfizer-BioNTech COVID-19 vaccine;
2. Known history of severe allergic reaction to any component of either the Moderna COVID-19 vaccine or Pfizer-BioNTech COVID-19 vaccine;
3. Thrombotic events, myocarditis, or pericarditis temporally associated with prior dose of COVID-19 vaccine;
4. Any change in transplant immunosuppression regimen (drug or dose) in response to suspected or proven rejection within the last 6 months;
5. Significant graft dysfunction;
6. Receipt of any cellular depleting agent (e.g. ATG, Rituximab, Alemtuzumab, Cyclophosphamide) within 12 months preceding enrollment;
7. Receiving systemic immunomodulatory medication(s) for any condition other than transplant;
8. Any untreated active infection, including BK viremia >10^4 copies;
9. Infection with human immunodeficiency virus (HIV);
10. Maintenance immunosuppressive regimen that includes belatacept or abatacept;
11. Recent (within one year) or ongoing treatment for malignancy; or
12. Any past or current medical problems, treatments, or findings which, in the opinion of the investigator, may pose additional risks from participation in the study, may interfere with the candidate's ability to comply with study requirements or may impact the quality or interpretation of the data obtained from the study.

The plan is to share data upon completion of the study in: Immunology Database and Analysis Portal (ImmPort), a long-term archive of clinical and mechanistic data from DAIT-funded grants and contracts.

On average, within 24 months after database lock for the trial.

Open access.

AEs are reported for 30 days post vaccine and SAEs for 6 months post vaccine.

Adverse Events temporally associated (24 hours) with the research blood draws and nasopharyngeal swabs will be collected from the time of the screening visit until a participant completes study participation.

Adverse Events as defined in Section 12.2.1 in the protocol will be collected for 30 days following COVID-19 vaccine administration. Serious Adverse Events will be collected for 6 months following vaccine administration.

No reported Serious Adverse Events were related to the vaccine.