During the Delta period, mildly elevated ALT was associated with increased risk of severe COVID-19 (N = 297, RR 1.42, 95% CI 1.08–1.88) but severely elevated ALT was associated with reduced risk of severe COVID-19 (N = 5, RR 4E−7, 95% CI 6E−8 – 3E−6). Here, GPT is linked to COVID-19.