Comparing the effectiveness of hand hygiene techniques in reducing the microbial load and covering hand surfaces in healthcare workers: Updated systematic review

•WHO 6-step technique effectively reduces bacterial load on hands.•Effectiveness of hand hygiene techniques in covering all hand surfaces is limited.•Evidence for the most effective and feasible hand hygiene technique is inconclusive.•Substantial heterogeneity exists in the body of evidence.•Hand hygiene technique studies require standardization.