Sir, we have read with great interest the correspondence of Challacombe et al. on the antiseptic efficacy of povidone-iodine (PVP-I) against SARS-CoV-2; we aim to demonstrate the potential prophylactic capacity of the new generation of uncomplexed molecular iodine (I2) mouthwashes.1

PVP-I has been a gold standard antiseptic for decades with proven efficacy against the previously identified beta coronaviruses; it was one of the first candidates for the emergency trials attempting to establish an additional layer of protection for frontline healthcare workers.2 The mechanism of action of PVP-I relies primarily on the free iodine component, which is bound to a large polyvinylpyrrolidone molecule (PVP) acting as a carrier to deliver I2 to target cells. However, the viricidal activity of PVP-I is highly associated with its I2 content: the commonly used 10% PVP-I can only deliver 1-3 ppm of I2 in a compound of more than 31,600 ppm of total iodine atoms. The high percentage of bounded 'non-active' iodine contributes to all the undesirable toxicological and staining properties of PVP-I.3

A new generation of iodine-based antiseptics 'super iodine' was initiated recently to overcome the compositional side effects of PVP-I. Therefore, ioTech International (Boca Raton, FL) produced a patented aqueous solution of I2 that contains over 100 times more I2 than PVP-I and comes in various forms ready for prophylactic use including mouthwash, nasal spray, and hand cleanser.4 Moreover, the non-bioactive iodine content was reduced from 31,600 ppm in PVP-I to several hundred in the new formula thus accelerating its effect, increasing its shelf-life, and minimising its potential irritancy and mucosal staining.

In comparison to several antiseptic mouthwashes, the new I2 formulas showed higher viricidal efficacy against coronaviruses and took as short as 30 seconds to inactivate alpha coronaviruses (229E) completely.4 The same was observed in Rhinovirus which was totally inactivated above the cytotoxicity level after exposure to the new I2 formula for 30 seconds.4

To the best of our knowledge, there is an ongoing randomised control trial at St. Joseph's Hospital University (Paterson, NJ) to evaluate the efficacy of I2 mouthwashes and nasal sprays in protecting frontline healthcare workers by reducing their susceptibility of getting infected by SARS-CoV-2. Therefore, we suggest more controlled trials to be initiated using I2 products to benefit from their potential superiority over conventional PVP-I mouthwashes.