Occurrence of severe COVID-19 in vaccinated transplant patients.

To the editor:

Vaccination plays a paramount role in the current coronavirus disease 2019 (COVID-19) pandemic response. Although mRNA-based vaccines elicit a strong immune response in the general population, the immunization rates of immunocompromised patients—including solid organ transplant recipients—have not been specifically investigated in mRNA-1273 and BNT162b2 pivotal trials. , This knowledge gap should be addressed urgently, as these patients are highly prone to developing severe COVID-19.

Here, we describe a total of 55 solid organ transplant recipients (52 kidney and 3 simultaneous kidney–pancreas) who developed COVID-19 after receiving 2 doses of mRNA-based severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) vaccines. A total of 9 and 46 patients received the mRNA-1273 (Moderna) and the BNT162b2 (Pfizer-BioNTech) vaccine, respectively. The study sample included 32 men and 23 women (median age: 60 years, interquartile range: 49−67 years; mean time from transplantation: 66 months, interquartile range: 33−138 months). Six patients were treated with belatacept, and 1 with rituximab. COVID-19 symptoms appeared after a median of 22 days after the second vaccine dose (interquartile range: 13−36 days; Figure 1 ). Of the 55 patients, 15 (27%) required hospitalization for oxygen therapy. Of these, 6 were admitted to an intensive care unit, and 3 died. Among the 25 patients with available data on anti–SARS-CoV-2 antibodies between the second vaccine dose and the onset of COVID-19 symptoms, 24 had negative serology, and 1 had positive results with weak antibodies levels (577 AU/L on the day of the second injection; Architect Abbot test). SARS-CoV-2 sequencing, which was performed in 24 cases, revealed 5 wild-type viruses, 17 UK variants, 1 Marseille variant, and one B 1.160 variant.

Figure 1

Time from the second vaccine dose to the onset of coronavirus disease 2019 (COVID-19) symptoms in each kidney transplant recipient. Y-axis represents each patient case. In all cases, the second dose was administered at a timepoint from February 8 to April 22, 2021. Green bars indicate patients who received the Moderna vaccine; blue bars indicate patients who received the Pfizer/BioNTech vaccine.

Growing evidence indicates that solid organ transplant recipients who receive mRNA-based vaccines have low immunization rates, with <50% of patients showing antibodies against the SARS-CoV-2 spike protein. , Although immunosuppressive drugs are thought to play a key role in this phenomenon, the occurrence of severe COVID-19 after mRNA-based vaccination in immunocompetent or immunocompromised subjects has not yet been reported. A potential explanation for persisting disease susceptibility may lie in an absent humoral response, coupled with a limited or insufficient T-cell response, even after the second vaccine dose.

Vulnerable immunocompromised patients who are nonresponsive to mRNA-based SARS-CoV-2 vaccines should undergo close serologic follow-up and/or maintain strict sanitary protection measures. Other management strategies may include priority vaccination of the patients’ households and the development of more-effective vaccination schemes.