Introduction: Since 30th December 2020, Singapore has embarked on an intensive mRNA COVID-19 vaccination program that has resulted in 95% and 70% of its eligible population receiving 2 and 3 doses of mRNA COVID-19 vaccine respectfully. However, the impact of mRNA COVID-19 vaccine on outcomes of COVID-19 infection in kidney transplant recipients from Asia remains unknown. This study seeks to determine the impact of mRNA COVID-19 vaccination on clinical outcomes and whether vaccination status can be used as a predictor for good outcomes.

Methodology: Singapore has undergone 4 waves of COVID-19 infection driven by imported cases (2020), outbreaks in foreign worker dormitories (2020), community spread by Delta Variant (2021) and Omicron Variant (2022). During this period, the renal transplant program at SGH set up a COVID-19 registry to prospectively collect data that could be analyzed to guide clinical policies and protocols. Data were analyzed according to number of mRNA vaccine doses given (group A - 3 doses vs. group B – 0 to 2 doses).

Results: Between 22nd June 2020 and 11TH March 2021, 163/864 (18.8%) of kidney transplant recipients followed up at SGH were infected with COVID-19. Among these, 119/163 (73.0%) and 44/163 (26.9%) were in group A and B respectfully. Patients in group A were significantly younger (56.1±11.3 vs. 60.4±11.8 years; p=0.03) with a lower 4C Mortality Score (4.5±2.8 vs. 6.0±3.4; p=0.008) but the Charlson Comorbidity Index Score were similar between group A and B (3.5±1.2 vs. 3.8±1.2; p=0.60). Among 155 patients who had anti-SARS CoV2 antibody levels measured, a greater proportion from group A than group B had protective levels of anti-SARS CoV2 antibodies (defined as ≿ 500 AU/mL) (44.7%; [n=51/114] vs. 24.4%; [n=10/41]; p=0.03). As there was no death or graft loss in this study population, the need for oxygen therapy was taken as a primary endpoint for the study which was less frequent in group A than group B (1.7%; [n=2/119] vs. 11.4%; [n=5/44]; p=0.019). Use of other therapeutics was lower in group A than in group B such as Remdesivir (42.8%; [n=51/119] vs. 63.6%; [n=28/44]; p=0.057) and Dexamethasone (1.7%; [n=2/119] vs. 9.1%; [n=4/44]; p=0.07). Acute kidney injury occurred less frequently in group A than B (7.6%; [n=9/119] vs. 20.5%; [n=9/44]; p=0.057) but the event rate for intensive care admission (1.7%; [n=2/119] vs. 2.3%; [n=1/44]; p=0.81) and cardiovascular events (2.5%; [n=3/119] vs. 4.5%; [n=2/44]; p=0.669) were low for both group A and B respectfully. On multivariate analysis, predictor of oxygen therapy was the 4C Mortality Score (aOR 1.5, 95% CI 1.12-2.02; p=0.001).

Conclusion: Kidney transplant recipients with 3 doses of mRNA COVID-19 vaccine benefited from higher frequency of protective antibody levels. However, it was the 4C Mortality Score that predicted the need for oxygen therapy instead of vaccination status.