Virucidal activity of Formulation I of the World Health Organization's alcohol-based handrubs: impact of changes in key ingredient levels and test parameters.

Background: A recently modified World Health Organization (WHO) Formulation I was examined as 80% and 97% solutions against poliovirus type 1, adenovirus type 5 and murine norovirus according to the new European Norm prEN 14476:2011. In a previous study the unmodified WHO Formulation I had failed to demonstrate a sufficient activity against poliovirus type 1 according to the European Norm EN 14476-2007 whereas a sufficient activity was seen with adeno- and norovirus.

Findings: The modified WHO Formulation I demonstrated a virucidal activity against all 3 test viruses of the European Norm prEN 14476:2011 under clean conditions. This was achieved as 80% solution against adeno- and norovirus within 30 seconds and as 97% solution against poliovirus within 60 seconds. Testing the unmodified WHO Formulation I against poliovirus type 1 in the 97% assay of the European Norm prEN 14476:2011 an identical activity could be demonstrated. When comparing the 80% and the 97% assay of the European Norm prEN 14476:2011 the modified WHO Formulation I as 80% solution was active against adenovirus type 5 within 30 seconds whereas the 97% solution failed within 2 minutes exposure time.

Conclusions: The technical possibility in the new European Norm prEN 14476:2011 allows testing a ready-to-use disinfectant as 97% solution and is responsible for the new virucidal claim of the modified WHO Formulation I. In contrast to the improvements with poliovirus type 1 the activity against adenovirus type 5 decreased when increasing the test concentration from 80% to 97%.