Studies have reported low seroconversion rates (58% after the second dose) in solid organ transplant recipients who received a messenger RNA (mRNA) SARS-CoV-2 vaccine. 1,2 Based on this evidence, the French National Authority for Health issued a recommendation in April 2021 to administer a third vaccine dose in immunosuppressed patients who did not respond after 2 doses. We examined the antibody responses of kidney transplant recipients who did not respond to 2 doses and received a third dose (100 μg) of the mRNA-1273 vaccine (Moderna).

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Data concerning the anti-SARS-CoV-2 antibody response after mRNA COVID-19 vaccine in kidney transplant recipients (KTRs) are currently lacking. Here, we sought to examine this issue by analyzing the serological response observed in 241 KTRs after a first vaccine injection. Our results indicate that KTRs have a weak anti-SARS-CoV-2 antibody response, ultimately resulting in a low seroconversion rate (26/241, 10.8%). This phenomenon likely stems from a high immunosuppression burden in this clinical population.

The cilgavimab−tixagevimab combination retains a partial in vitro neutralizing activity against the current SARS‐CoV‐2 variants of concern (omicron BA.1, BA.1.1, and BA.2). Here, we examined whether preexposure prophylaxis with cilgavimab−tixagevimab can effectively protect kidney transplant recipients (KTRs) against the omicron variant. Of the 416 KTRs who received intramuscular prophylactic injections of 150 mg tixagevimab and 150 mg cilgavimab, 39 (9.4%) developed COVID‐19. With the exception of one case, all patients were symptomatic. Hospitalization and admission to an intensive care unit were required for 14 (35.9%) and three patients (7.7%), respectively. Two KTRs died of COVID‐19‐related acute respiratory distress syndrome. SARS‐CoV‐2 sequencing was carried out in 15 cases (BA.1, n = 5; BA.1.1, n = 9; BA.2, n = 1). Viral neutralizing activity of the serum against the BA.1 variant was negative in the 12 tested patients, suggesting that this prophylactic strategy does not provide sufficient protection against this variant of concern. In summary, preexposure prophylaxis with cilgavimab−tixagevimab at the dose of 150 mg of each antibody does not adequately protect KTRs against omicron. Further clarification of the optimal dosing can assist in our understanding of how best to harness its protective potential.