BACKGROUND: Systemic corticosteroids are used to treat people with COVID-19 because they counter hyper-inflammation. Existing evidence syntheses suggest a slight benefit on mortality. Nonetheless, size of effect, optimal therapy regimen, and selection of patients who are likely to benefit most are factors that remain to be evaluated. OBJECTIVES: To assess whether and at which doses systemic corticosteroids are effective and safe in the treatment of people with COVID-19, to explore equity-related aspects in subgroup analyses, and to keep up to date with the evolving evidence base using a living systematic review approach. SEARCH METHODS: We searched the Cochrane COVID-19 Study Register (which includes PubMed, Embase, CENTRAL, ClinicalTrials.gov, WHO ICTRP, and medRxiv), Web of Science (Science Citation Index, Emerging Citation Index), and the WHO COVID-19 Global literature on coronavirus disease to identify completed and ongoing studies to 6 January 2022. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that evaluated systemic corticosteroids for people with COVID-19. We included any type or dose of systemic corticosteroids and the following comparisons: systemic corticosteroids plus standard care versus standard care, different types, doses and timings (early versus late) of corticosteroids. We excluded corticosteroids in combination with other active substances versus standard care, topical or inhaled corticosteroids, and corticosteroids for long-COVID treatment. DATA COLLECTION AND ANALYSIS: We followed standard Cochrane methodology. To assess the risk of bias in included studies, we used the Cochrane 'Risk of bias' 2 tool for RCTs. We rated the certainty of the evidence using the GRADE approach for the following outcomes: all-cause mortality up to 30 and 120 days, discharged alive (clinical improvement), new need for invasive mechanical ventilation or death (clinical worsening), serious adverse events, adverse events, hospital-acquired infections, and invasive fungal infections. MAIN RESULTS: We included 16 RCTs in 9549 participants, of whom 8271 (87%) originated from high-income countries. A total of 4532 participants were randomised to corticosteroid arms and the majority received dexamethasone (n = 3766). These studies included participants mostly older than 50 years and male. We also identified 42 ongoing and 23 completed studies lacking published results or relevant information on the study design. Hospitalised individuals with a confirmed or suspected diagnosis of symptomatic COVID-19 Systemic corticosteroids plus standard care versus standard care plus/minus placebo We included 11 RCTs (8019 participants), one of which did not report any of our pre-specified outcomes and thus our analyses included outcome data from 10 studies. Systemic corticosteroids plus standard care compared to standard care probably reduce all-cause mortality (up to 30 days) slightly (risk ratio (RR) 0.90, 95% confidence interval (CI) 0.84 to 0.97; 7898 participants; estimated absolute effect: 274 deaths per 1000 people not receiving systemic corticosteroids compared to 246 deaths per 1000 people receiving the intervention (95% CI 230 to 265 per 1000 people); moderate-certainty evidence). The evidence is very uncertain about the effect on all-cause mortality (up to 120 days) (RR 0.74, 95% CI 0.23 to 2.34; 485 participants). The chance of clinical improvement (discharged alive at day 28) may slightly increase (RR 1.07, 95% CI 1.03 to 1.11; 6786 participants; low-certainty evidence) while the risk of clinical worsening (new need for invasive mechanical ventilation or death) may slightly decrease (RR 0.92, 95% CI 0.84 to 1.01; 5586 participants; low-certainty evidence). For serious adverse events (two RCTs, 678 participants), adverse events (three RCTs, 447 participants), hospital-acquired infections (four RCTs, 598 participants), and invasive fungal infections (one study, 64 participants), we did not perform any analyses beyond the presentation of descriptive statistics due to very low-certainty evidence (high risk of bias, heterogeneous definitions, and underreporting). Different types, dosages or timing of systemic corticosteroids We identified one RCT (86 participants) comparing methylprednisolone to dexamethasone, thus the evidence is very uncertain about the effect of methylprednisolone on all-cause mortality (up to 30 days) (RR 0.51, 95% CI 0.24 to 1.07; 86 participants). None of the other outcomes of interest were reported in this study. We included four RCTs (1383 participants) comparing high-dose dexamethasone (12 mg or higher) to low-dose dexamethasone (6 mg to 8 mg). High-dose dexamethasone compared to low-dose dexamethasone may reduce all-cause mortality (up to 30 days) (RR 0.87, 95% CI 0.73 to 1.04; 1269 participants; low-certainty evidence), but the evidence is very uncertain about the effect of high-dose dexamethasone on all-cause mortality (up to 120 days) (RR 0.93, 95% CI 0.79 to 1.08; 1383 participants) and it may have little or no impact on clinical improvement (discharged alive at 28 days) (RR 0.98, 95% CI 0.89 to 1.09; 200 participants; low-certainty evidence). Studies did not report data on clinical worsening (new need for invasive mechanical ventilation or death). For serious adverse events, adverse events, hospital-acquired infections, and invasive fungal infections, we did not perform analyses beyond the presentation of descriptive statistics due to very low-certainty evidence. We could not identify studies for comparisons of different timing and systemic corticosteroids versus other active substances. Equity-related subgroup analyses We conducted the following subgroup analyses to explore equity-related factors: sex, age (< 70 years; ≥ 70 years), ethnicity (Black, Asian or other versus White versus unknown) and place of residence (high-income versus low- and middle-income countries). Except for age and ethnicity, no evidence for differences could be identified. For all-cause mortality up to 30 days, participants younger than 70 years seemed to benefit from systemic corticosteroids in comparison to those aged 70 years and older. The few participants from a Black, Asian, or other minority ethnic group showed a larger estimated effect than the many White participants. Outpatients with asymptomatic or mild disease There are no studies published in populations with asymptomatic infection or mild disease. AUTHORS' CONCLUSIONS: Systemic corticosteroids probably slightly reduce all-cause mortality up to 30 days in people hospitalised because of symptomatic COVID-19, while the evidence is very uncertain about the effect on all-cause mortality up to 120 days. For younger people (under 70 years of age) there was a potential advantage, as well as for Black, Asian, or people of a minority ethnic group; further subgroup analyses showed no relevant effects. Evidence related to the most effective type, dose, or timing of systemic corticosteroids remains immature. Currently, there is no evidence on asymptomatic or mild disease (non-hospitalised participants). Due to the low to very low certainty of the current evidence, we cannot assess safety adequately to rule out harmful effects of the treatment, therefore there is an urgent need for good-quality safety data. Findings of equity-related subgroup analyses should be interpreted with caution because of their explorative nature, low precision, and missing data. We identified 42 ongoing and 23 completed studies lacking published results or relevant information on the study design, suggesting there may be possible changes of the effect estimates and certainty of the evidence in the future.