Evaluation of Alcohol-Based Hand Sanitizers by U.S. and European In Vivo Methodologies: Formulation Matters

Background: Hand hygiene is recognized as one of the most important measures for preventing HAIs.  In the past decade, use of alcohol-based hand sanitizers (ABHS) has become standard practice for hand hygiene in U.S. hospitals.  Previous publications have suggested that alcohol concentrations above 75% are necessary to meet global efficacy standards for hand sanitizers and have questioned the ability of ABHS foams and gels to meet these requirements. 

Objective: To determine the influence of alcohol content, product format (gel or foam), and product formulation on the in vivo antibacterial efficacy of ABHS measured according to U.S. and EU standard test methodologies.

Methods: Test products included 4 ABHS: Test product A (62% ethanol gel), Test Product B (70% ethanol gel), Test Product C (novel, patent pending 70% ethanol gel), and Test Product D (novel, patent pending 70% ethanol foam).  Test products were evaluated on the hands of adult subjects using the Health Care Personnel Hand Wash (HCPHW) method based on U.S. FDA requirements; and European Norm, EN 1500, which is required for hygienic hand rubs in the EU. Log reductions were calculated after one application and ten applications with the HCPHW method and after a single application with EN 1500.

Results: All 4 test products met EN 1500 requirements at a volume of 3 ml, rubbed for 30 seconds; demonstrating non-inferiority to the 60% isopropanol reference product.  When tested at a volume of approximately 5 ml by the HCPHW method, Test Products B, C and D met FDA HCPHW requirements, achieving log₁₀ reductions of 4.22, 3.99, and 4.14 after one application and 3.32, 5.40, and 5.45 after ten applications, respectively.  Test products C and D were statistically superior to Test product B at the tenth application.  Additionally, Test Products C and D met HCPHW requirements when tested at a more realistic 3 ml application volume, obtaining log₁₀ reductions of 3.88 and 3.99 at Application 1, and log₁₀ reductions of 4.47 and 4.70 at Application 10, respectively.

Conclusions: Contrary to previous speculation, ABHS with ethanol concentrations as low as 70% were able to meet global efficacy requirements.  In fact, a 62% ethanol ABHS was capable of meeting EN1500 requirements.  The U.S. HCPHW requirements are more stringent than EN1500, with the requirement for a 3 log reduction after 10 applications being the greatest challenge.  Product formulation was found to be a critical determinant of antibacterial efficacy, as optimally formulated ABHS (Products C and D) were able to meet HCPHW at lower volumes than a traditional ABHS containing the same level of alcohol.  Finally, contrary to previous speculations, the foam format does not compromise product performance, as the performance of optimally formulated gel (Product C) and foam (Product D) ABHS exhibited equivalent efficacy by both methodologies.