Ivermectin, an antiparasitic agent, inhibits the replication of viruses in vitro. The molecular hypothesis of ivermectin’s antiviral mode of action suggests an inhibitory effect on severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) replication in early stages of infection. Currently, evidence on ivermectin for prevention of SARS‐CoV‐2 infection and COVID‐19 treatment is conflicting.
To assess the efficacy and safety of ivermectin plus standard of care compared to standard of care plus/minus placebo, or any other proven intervention for people with COVID‐19 receiving treatment as inpatients or outpatients, and for prevention of an infection with SARS‐CoV‐2 (postexposure prophylaxis).
We searched the Cochrane COVID‐19 Study Register, Web of Science (Emerging Citation Index and Science Citation Index), WHO COVID‐19 Global literature on coronavirus disease, and HTA database weekly to identify completed and ongoing trials without language restrictions to 16 December 2021. Additionally, we included trials with > 1000 participants up to April 2022.
We included randomized controlled trials (RCTs) comparing ivermectin to standard of care, placebo, or another proven intervention for treatment of people with confirmed COVID‐19 diagnosis, irrespective of disease severity or treatment setting, and for prevention of SARS‐CoV‐2 infection. Co‐interventions had to be the same in both study arms.
For this review update, we reappraised eligible trials for research integrity: only RCTs prospectively registered in a trial registry according to WHO guidelines for clinical trial registration were eligible for inclusion.
Data collection and analysis
We assessed RCTs for bias, using the Cochrane RoB 2 tool. We used GRADE to rate the certainty of evidence for outcomes in the following settings and populations: 1) to treat inpatients with moderate‐to‐severe COVID‐19, 2) to treat outpatients with mild COVID‐19 (outcomes: mortality, clinical worsening or improvement, (serious) adverse events, quality of life, and viral clearance), and 3) to prevent SARS‐CoV‐2 infection (outcomes: SARS‐CoV‐2 infection, development of COVID‐19 symptoms, admission to hospital, mortality, adverse events and quality of life).
We excluded seven of the 14 trials included in the previous review version; six were not prospectively registered and one was non‐randomized. This updated review includes 11 trials with 3409 participants investigating ivermectin plus standard of care compared to standard of care plus/minus placebo. No trial investigated ivermectin for prevention of infection or compared ivermectin to an intervention with proven efficacy. Five trials treated participants with moderate COVID‐19 (inpatient settings); six treated mild COVID‐19 (outpatient settings). Eight trials were double‐blind and placebo‐controlled, and three were open‐label. We assessed around 50% of the trial results as low risk of bias.
We identified 31 ongoing trials. In addition, there are 28 potentially eligible trials without publication of results, or with disparities in the reporting of the methods and results, held in ‘awaiting classification’ until the trial authors clarify questions upon request.
Ivermectin for treating COVID‐19 in inpatient settings with moderate‐to‐severe disease
We are uncertain whether ivermectin plus standard of care compared to standard of care plus/minus placebo reduces or increases all‐cause mortality at 28 days (risk ratio (RR) 0.60, 95% confidence interval (CI) 0.14 to 2.51; 3 trials, 230 participants; very low‐certainty evidence); or clinical worsening, assessed by participants with new need for invasive mechanical ventilation or death at day 28 (RR 0.82, 95% CI 0.33 to 2.04; 2 trials, 118 participants; very low‐certainty evidence); or serious adverse events during the trial period (RR 1.55, 95% CI 0.07 to 35.89; 2 trials, 197 participants; very low‐certainty evidence). Ivermectin plus standard of care compared to standard of care plus placebo may have little or no effect on clinical improvement, assessed by the number of participants discharged alive at day 28 (RR 1.03, 95% CI 0.78 to 1.35; 1 trial, 73 participants; low‐certainty evidence); on any adverse events during the trial period (RR 1.04, 95% CI 0.61 to 1.79; 3 trials, 228 participants; low‐certainty evidence); and on viral clearance at 7 days (RR 1.12, 95% CI 0.80 to 1.58; 3 trials, 231 participants; low‐certainty evidence). No trial investigated quality of life at any time point.
Ivermectin for treating COVID‐19 in outpatient settings with asymptomatic or mild disease
Ivermectin plus standard of care compared to standard of care plus/minus placebo probably has little or no effect on all‐cause mortality at day 28 (RR 0.77, 95% CI 0.47 to 1.25; 6 trials, 2860 participants; moderate‐certainty evidence) and little or no effect on quality of life, measured with the PROMIS Global‐10 scale (physical component mean difference (MD) 0.00, 95% CI ‐0.98 to 0.98; and mental component MD 0.00, 95% CI ‐1.08 to 1.08; 1358 participants; high‐certainty evidence). Ivermectin may have little or no effect on clinical worsening, assessed by admission to hospital or death within 28 days (RR 1.09, 95% CI 0.20 to 6.02; 2 trials, 590 participants; low‐certainty evidence); on clinical improvement, assessed by the number of participants with all initial symptoms resolved up to 14 days (RR 0.90, 95% CI 0.60 to 1.36; 2 trials, 478 participants; low‐certainty evidence); on serious adverse events (RR 2.27, 95% CI 0.62 to 8.31; 5 trials, 1502 participants; low‐certainty evidence); on any adverse events during the trial period (RR 1.24, 95% CI 0.87 to 1.76; 5 trials, 1502 participants; low‐certainty evidence); and on viral clearance at day 7 compared to placebo (RR 1.01, 95% CI 0.69 to 1.48; 2 trials, 331 participants; low‐certainty evidence). None of the trials reporting duration of symptoms were eligible for meta‐analysis.
For outpatients, there is currently low‐ to high‐certainty evidence that ivermectin has no beneficial effect for people with COVID‐19. Based on the very low‐certainty evidence for inpatients, we are still uncertain whether ivermectin prevents death or clinical worsening or increases serious adverse events, while there is low‐certainty evidence that it has no beneficial effect regarding clinical improvement, viral clearance and adverse events. No evidence is available on ivermectin to prevent SARS‐CoV‐2 infection. In this update, certainty of evidence increased through higher quality trials including more participants. According to this review’s living approach, we will continually update our search.
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