Sir, a recent letter in your journal by Challacombe et al. highlighted the potential of povidone iodine (PVP-I) mouthwash and nasal spray in reducing the risk of cross-infection of COVID-19 among the dentists and their assistants.1 The evidence used was based on in vitro data of PVP-I's virucidal activity against coronaviruses such as SARS-CoV and MERS-CoV. Here, we demonstrate in vitro virucidal activity of an oral PVP-I product against SARS-CoV-2, the virus causing COVID-19.

BETADINE Gargle and Mouth Wash in two concentrations, undiluted (PVP-I 1% w/v) and at a 1:2 dilution (PVP-I 0.5% w/v) was tested for virucidal activity (≥4 log10 reduction in viral titres) against SARS-CoV-2 in both clean (0.3 g/l BSA) and dirty (3.0 g/l BSA + 3 mL/L human erythrocytes) conditions at time points of 15, 30 and 60 seconds in a BSL-3 laboratory of the Tropical Infectious Diseases Research and Education Center (TIDREC), University of Malaya, Malaysia. The SARS-CoV-2 was isolated and propagated in Vero-E6 cells in TIDREC. The cytotoxicity of the product to the Vero-E6 cells was evaluated and taken into account when performing the kill time assay. Virus kill time assay was performed based on the established EN14476 methodology.2 Virus titres were calculated as 50% tissue culture infectious dose (TCID50/mL) using the Spearman-Karber method.2 The study demonstrated that undiluted PVP-I achieved >5 log10 reduction in the virus titres at 15, 30 and 60 seconds treatment exposure under both clean and dirty conditions. In contrast, when PVP-I was tested at 1:2 dilution a >4 log10 kill at 15 seconds and >5 log10 kill at 30 and 60 seconds in comparison to control was seen in both clean and dirty.

Dental practice poses a potential risk of COVID-19 cross-infection among patients, dentists and their assistants through direct exposure to saliva and indirect contact through contaminated instruments.3 Several associations, including the Australian Dental Association, have recommended using a preprocedural mouthwash with products such as povidone iodine.4 In our study, we present direct evidence of the virucidal activity of PVP-I gargle and against SARS-CoV-2 in just 15 seconds. In today's scenario, PVP-I gargle and mouthwash could be an adjuvant to PPEs in reducing the risk of COVID-19 transmission in healthcare practices, especially when oral interventions are warranted, such as in dental practice.