Outcomes of SARS-CoV-2 Infection in Unvaccinated Compared with One or Two Dose Vaccinated Solid Organ Transplant Recipients: A Multicenter, Matched Cohort Study

V. G. Hall¹, G. Alahmadi², J. T. Solera², T. Marinelli², H. Cardinal³, G. Ramesh Prasad⁴, S. A. De Serres⁵, D. Isaac⁶, R. Mainra⁷, C. Lamarche⁸, R. Sapir-Pichhadze⁹, S. Gilmour¹⁰, J. Matelski², A. Humar², D. Kumar²

¹University Health Network/Toronto General Hospital, Toronto, ON, Canada, ²UHN, Toronto, ON, Canada, ³Department of Medicine, UMontreal, Montreal, QC, Canada, ⁴Kidney Transplant Program, St. Michael's Hospital, Toronto, ON, Canada, ⁵Transplantation Unit, Renal division, Laval University, Quebec, QC, Canada, ⁶Division of Transplant Medicine, University of Calgary, Calgary, AB, Canada, ⁷University Health Center of Saskatchewan, Saskatoon, SK, Canada, ⁸Hôpital Maisonneuve-Rosemont Research Institute, Montreal, QC, Canada, ⁹McGill University, Montreal, QC, Canada, ¹⁰Stollery Children's Hospital, Edmonton, AB, Canada

Meeting: 2022 American Transplant Congress

Abstract number: 166

Keywords: COVID-19, Infection, Multicenter studies, Vaccination

Topic: Clinical Science » Infection Disease » 24 - All Infections (Excluding Kidney & Viral Hepatitis)

Session Information

Session Name: COVID-19 Infections Part 1: All Organs

Session Type: Rapid Fire Oral Abstract

Date: Sunday, June 5, 2022

Session Time: 5:30pm-7:00pm

Presentation Time: 6:50pm-7:00pm

Location: Hynes Ballroom B

*Purpose: It is unknown if vaccine breakthrough COVID-19 infections are milder or as severe as infections in unvaccinated solid organ transplant (SOT) recipients.

*Methods: We performed a multicenter matched cohort study between March 2020 – September 2021 across 9 transplant programs in Canada, to assess influence of COVID-19 vaccination on outcomes of COVID-19 infection. Participants with breakthrough infection, who had received at least one dose of vaccine were compared with participants who developed COVID-19 infection but were unvaccinated. Propensity score matching was used to match the two cohorts for age, sex, transplant type and number of comorbidities. Logistic regression modelling was performed to assess the influence of vaccination status on disease severity outcomes. Two models were utilized (Table 1), Model 1 (^) compared any vaccination vs no vaccination; whereas Model 2 (*) used a numeric predictor (0, 1 or 2 doses to estimate an odds ratio for a 1 dose reduction).

*Results: After matching, there were a total of 297 patients, with 77 one or two dose vaccinated patients matched to 220 unvaccinated. There were no significant differences in any disease severity outcome (Table 1) amongst medically attended vaccine breakthroughs compared with unvaccinated participants, including mortality. The use of dexamethasone, remdesivir and antibiotics were similar in the two groups; however, tocilizumab had been used more frequently in the vaccinated group (15/77 (19.5%) vs 5/220 (2.3%), p = <0.001).

*Conclusions: SOT recipients who develop medically-attended COVID-19 following 1- or 2-dose mRNA vaccine appear to have similar disease severity to unvaccinated patients who develop infection. Alternate strategies, including booster vaccinations or monoclonal antibody prophylaxis should be studied in this vulnerable population.

Table 1.Disease severity outcomes in vaccinated compared with unvaccinated SOTr with COVID-19
Outcomes	Vaccinated (n=77), n, %	Unvaccinated (n=220), n, %	Odds ratio, 95% Confidence Interval
Oxygen^	29 (37.7)	78 (35.5)	1.21 (0.61 – 2.38)
Acute Kidney Injury^	12 (15.6)	43 (19.5)	1.49 (0.63 – 3.50)
ICU admission*	18 (23.4)	30 (13.6)	0.72 (0.46 – 1.13)
Ventilator*	11 (14.3)	25 (11.4)	0.88 (0.52 – 1.48)
All-cause mortality*	7 (9.1)	26 (11.8)	1.19 (0.64 – 2.22)
COVID-19 related mortality*	6 (7.8)	25 (11.4)	1.34 (0.68 – 2.63)

To cite this abstract in AMA style:

Hall VG, Alahmadi G, Solera JT, Marinelli T, Cardinal H, Prasad GRamesh, Serres SADe, Isaac D, Mainra R, Lamarche C, Sapir-Pichhadze R, Gilmour S, Matelski J, Humar A, Kumar D. Outcomes of SARS-CoV-2 Infection in Unvaccinated Compared with One or Two Dose Vaccinated Solid Organ Transplant Recipients: A Multicenter, Matched Cohort Study [abstract]. Am J Transplant. 2022; 22 (suppl 3). https://atcmeetingabstracts.com/abstract/outcomes-of-sars-cov-2-infection-in-unvaccinated-compared-with-one-or-two-dose-vaccinated-solid-organ-transplant-recipients-a-multicenter-matched-cohort-study/. Accessed May 18, 2025.

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