Association Between SARS-CoV-2 Messenger RNA Vaccines and Lower Infection Rates in Kidney Transplant Recipients : A Registry-Based Report

Abstract

Background: The real-world protection provided by SARS-CoV-2 messenger RNA (mRNA) vaccines to kidney transplant recipients (KTRs) remains uncertain.

Objective: To study the association between mRNA vaccination and SARS-CoV-2 infection rate in KTRs.

Design: Retrospective observational cohort study.

Setting: The Czech Republic (17 February to 16 May 2021).

Patients: 2101 KTRs followed in the Department of Nephrology at the Institute for Clinical and Experimental Medicine.

Measurements: Positive result for SARS-CoV-2 on polymerase chain reaction test and vaccination status of KTRs.

Results: The incidence rate in the vaccinated group was 0.474 per 1000 person-days (33 cases in 69 672 days at risk). The incidence rate in the unvaccinated group was 1.370 per 1000 person-days (79 cases in 57 658 days at risk). The unadjusted incidence rate ratio (IRR; incidence rate of vaccinated/incidence rate of unvaccinated) for KTRs was 0.346 (95% CI, 0.227 to 0.514). The multivariable adjusted IRR for KTRs was 0.544 (CI, 0.324 to 0.876).

Limitation: Retrospective observational design, uneven follow-up of patient groups, and different exposition to SARS-CoV-2 stemming from strong temporal trends and differences in clinical and probably behavioral characteristics.

Conclusion: Vaccination of KTRs is associated with lower risk for SARS-CoV-2 infection.

Primary funding source: The Ministry of Health of the Czech Republic.

Visual Abstract.. SARS-CoV-2 Messenger RNA Vaccines in Kidney Transplant Recipients.

The authors compared the rate of SARS-CoV-2 infection in kidney transplant recipients among those who did and did not receive a messenger RNA vaccine in the Czech Republic between February and May 2021 while the Alpha variant was predominant.

Figure 1.. Flow chart of study participants.

Overall, 2479 KTRs with functional grafts were considered for inclusion to the study. To establish a SARS-CoV-2–naive cohort, patients with previous positive results for SARS-CoV-2 infection were excluded, as were patients vaccinated with non–messenger RNA vaccines. In total, 2101 KTRs were considered as the SARS-CoV-2–naive cohort. Of these, 1601 KTRs contributed at least part of their follow-up time to the unvaccinated days at risk, whereas 500 did not contribute. These were the KTRs vaccinated between 13 January and 17 February, 6 of whom did not finish vaccination and thus did not contribute to any days at risk, and 494 of whom entered the study denoted as unfinished vaccination but afterward reached full vaccination status and, therefore, contributed only toward vaccinated days at risk. A total of 246 KTRs did not finish full vaccination because they had a positive result for SARS-CoV-2 infection after the first dose (n = 28), they did not receive the second dose for other reasons (n = 5), or they received the first dose before the end of the study period but reached full vaccination status after its end (n = 213). Kidney transplant recipients who did not finish full vaccination contributed to the unvaccinated days at risk and were censored at the day of first vaccine dose. A total of 1509 reached full vaccination and contributed toward vaccination days at risk; of these, 33 became positive for SARS-CoV-2 during the study period. A total of 346 were unvaccinated by the end of the study period, and 79 of them became positive for SARS-CoV-2 during the study period. KTR = kidney transplant recipient; PCR = polymerase chain reaction.

Figure 2.. Seven-day moving average of new cases per 100 000 persons in the Czech Republic and the United States.

The shaded area denotes the study period. The red and blue lines denote new cases per 100 000 persons in the Czech Republic and the United States, respectively. The green line represents the cumulative proportion of fully vaccinated KTRs during the study period. KTR = kidney transplant recipient.

Figure 3.. Incidence of COVID-19 during the study period for the unvaccinated and vaccinated KTRs, along with the general population.

The incidence for each group is computed as the number of new cases divided by the number of persons at risk for that group. The values are smoothed using 14-d moving average. KTR = kidney transplant recipient.