Summary of findings 1. Anticoagulants (all types) compared to no treatment for people hospitalised with COVID‐19.

Anticoagulants (all types) compared to no treatment for people hospitalised with COVID‐19
Patient or population: people hospitalised with COVID‐19 Setting: hospital (ICU and ward) Intervention: anticoagulants (all types) Comparison: no treatment
Outcomes	Impact	№ of participants (studies)	Certainty of the evidence (GRADE)
All‐cause mortality Follow‐up: range 8 to 28 days	One study reported reduction of mortality by OR adjusted for confounding (reduction of 58% on chance of death; 2075 participants). One study reported reduction of mortality only in a subgroup of severely ill participants (HR 0.86, 95% CI 0.82 to 0.89; 395 participants). Three studies reported no differences by adjusted OR (1.64, 95% CI 0.92 to 2.92; 449 participants), unadjusted OR (1.66, 95% CI 0.76 to 3.64; 154 participants) or adjusted RR (1.15, 95% CI 0.29 to 2.57; 192 participants). One study reported zero events in both intervention groups.	5685 (6 retrospective NRS)	⊕⊝⊝⊝ Very lowa,b,c
Necessity for additional respiratory support	No study measured this outcome
Mortality related to COVID‐19	No study measured this outcome
Deep vein thrombosis	No study measured this outcome
Pulmonary embolism	No study measured this outcome
Major bleeding Follow‐up: not reported	One study reported 24 (3%) bleeding events in the intervention group and 38 (1.9%) bleeding events in the control group (OR 1.62, 95% CI 0.96 to 2.71).	2773 (1 retrospective NRS)	⊕⊕⊝⊝ Lowc,d
CI: confidence interval; HR: hazard ratio; ICU: intensive care unit; NRS: non‐randomised studies; OR: odds ratio; RR: risk ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

^aDowngraded one level due to study limitations. Overall critical/serious risk of bias across studies, especially related to confounding.
^bDowngraded one level due to inconsistency. We decided not to pool data due to the heterogeneity of studies (especially due to differences in interventions).
^cDowngraded one level due to imprecision. Narrative synthesis was conducted with imprecise estimates.
^dDowngraded one level due to study limitations. Overall serious risk of bias, especially related to confounding.