Innovation, much of it depending on the transition of cutting-edge and/or existing technologies into action, has been a backbone of the response to the coronavirus disease 2019 (COVID-19) pandemic. As a result, an unprecedented number of vaccines, diagnostic tests, and therapeutics have been developed. Some of these are still in clinical trials, while others are licensed and widely used. It is no longer a question of when an effective vaccine or diagnostic test will be licensed, but rather how equitable distribution can occur through the Access to COVID-19 Tools Accelerator and the CoVax facility.¹

Innovation is also occurring in support of other pandemic needs, including decontamination of personal protective equipment (PPE) such as filtering facepiece respirators (FFRs) and medical masks (MMs). Severe PPE shortages early in the pandemic resulted in the issuance of guidance and strategies to optimize their use.^2–4 The PPE shortages led to rationing, often resulting in healthcare workers being issued 1 set of single-use PPE to be worn across multiple shifts, creating an enhanced risk of cross and self-contamination.^{Reference Srinivas, Maanasa and Meenakshi5–Reference O’Neal, Heisler, Mishori and Haar7}

As a result, urgent calls were issued by the European Union, the United Kingdom, and the US Food and Drug Administration (FDA) for safe and accessible methods to decontaminate used single-use FFRs and MMs. Research that addressed this need resulted in an array of procedures that use interventions such as vaporized hydrogen peroxide (VHP), ultraviolet light, ozone, or steam. Among these procedures, 13 have now been licensed for use in decontaminating PPE under the US FDA Emergency Use Authorization Act.⁸ They are being used in various decontamination systems that turn around large batches of PPE for reuse. Because most of these procedures require specialized equipment and a steady power supply, they can result in a cost of up to US$1.47 to disinfect just one single mask,^{Reference Weinheimer, Ellsworth and Ferguson9} a cost easily afforded by high-income countries. As with other innovations, however, there has not been equitable distribution of the necessary decontamination supplies and equipment to ensure safe reuse of PPE in some low- and middle-income countries.

In this issue of Infection Control and Hospital Epidemiology, Lendvay et al^{Reference Lendvay, Chen and Harcourt10} and the Determination of Methods for Mask and N95 Decontamination (DeMaND) study group report on an innovative approach to decontaminate PPE that provides a potential new use of methylene blue (MB), a positively charged phenothiazinium dye first synthesized in 1876 as a textile dye.^{Reference Wainwright and Crossley11}

Methylene blue belongs to a class of photosensitive chemicals that react when exposed to visible light by generating singlet oxygen molecules that damage viruses, bacteria, and lipidated membranes. MB is included on the WHO Model List of Essential Medicines for use as a microbicide for treatment of periodontal disease.¹² Recently, the effectiveness of the photochemical properties of MB in disinfecting severe acute respiratory coronavirus virus 2 (SARS-CoV-2) and surrogate viruses in plasma used as treatment have been documented,^{Reference Duan, Liu and Li13,Reference Jin, Yu and Zhang14} as well as its mode of action by attachment to the SARS-CoV-2 ACE-2 receptor.^{Reference Bojadzic, Alcazar and Buchwald15}

Based on these findings, the DeMaND study group has tested the hypotheses that MB with ordinary light exposure is effective in inactivating coronaviruses on PPE. The results of their study clearly show that MB has a decontamination effect on 3 different coronaviruses and that the integrity of PPE is stable when subjected to repeated (×5) cycles of MB decontamination. Its effectiveness lasts up to 8 hours, suggesting that MB with light activation is an effective means of decontaminating PPE for reuse.

As SARS-CoV-2 continues toward endemicity, lower-resource countries will require sustainable supplies of PPE should current shortages continue. Currently approved decontamination procedures may not be a sustainable solution to address this problem in some low- and middle-income countries, and MB decontamination—a known and safe product that can be applied in all settings—may provide a solution.

The potential of MB with photoactivations from natural light, at a cost of $0.33/L of 10 μM solution to decontaminate 125 masks (based on the protocol reported by Lendvay et al) could be the solution for PPE decontamination without specialized equipment. This possibility should be further studied for its potential as a preventive application on surfaces and pre-treated PPE. Concurrently, study of its effectiveness as a decontaminant for other pathogens, such as Ebola, Lassa, and other novel viruses, should also be studied.