Bias as a source of inconsistency in ivermectin trials for COVID-19: A systematic review. Ivermectin's suggested benefits are mainly based on potentially biased results.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 34933115 · doi:10.1016/j.jclinepi.2021.12.018
What was done
Authors conducted a systematic review and random-effects pairwise meta-analysis of randomized controlled trials (RCTs) evaluating ivermectin for the prevention and treatment of COVID-19, searching the L.OVE platform through July 6, 2021. Evidence certainty was assessed with GRADE, and sensitivity analyses were performed excluding trials evaluated as having high risk of bias or some methodological concerns.
What was found
The review included 29 RCTs with 5,592 participants. While unadjusted analyses (rated very low to low certainty) initially suggested benefits, removing trials with high risk of bias or methodological concerns eliminated effect estimates: ivermectin showed no meaningful reduction in mortality (risk difference [RD] 7 fewer deaths per 1,000; low certainty) or mechanical ventilation (RD 6 more per 1,000; low certainty), and probably did not improve symptom resolution (RD 14 more per 1,000; moderate certainty) or viral clearance (RD 12 fewer per 1,000; moderate certainty).
Why it matters
This review demonstrates that reported clinical benefits of ivermectin in earlier meta-analyses were driven primarily by studies with severe methodological limitations and high risk of bias rather than genuine therapeutic efficacy.
Limits
The search window captured trials only through July 2021. Primary studies had substantial methodological flaws, leaving low- to moderate-certainty evidence even after restricting to higher-quality trials, and prophylactic efficacy in exposed individuals remained uncertain.
Cited by
- contradicts In a systematic meta-analysis of ivermectin clinical trials for COVID-19, the only consistent finding across studies was a reduction in time to negative PCR (faster viral clearance).