## 1 Introduction  
As the spread of the new coronavirus affects social life worldwide, vaccines and antiviral agents should be immediately developed. In the future, living environments should be improved as a preventive measure. As coronavirus has an envelope structure, alcohol and hypochlorous acid are extensively used to some effect [1; 2]. However, the frequent use of antibacterial agents has recently caused resistant bacteria (e.g., methicillin-resistant _Staphylioccus aureus_ (MRSA)). Antiviral agents may have adverse effects when frequently applied to mutable RNA viruses [3; 4]. Therefore, safe, secure, and environmentally friendly active substances with different mechanisms of action should be developed in the long run.  
Polyoxometalates (PMs) are transition metal-oxide clusters, a series of hundreds of compounds created by substituting metal elements and modifying their three-dimensional structures [5]. Their biological activities have become predictable based on their three-dimensional structures [5]. Of the PMs with antitumor, antiviral, antibacterial, or other activities, antiviral PMs have been investigated regarding their activities and mechanisms of action [6,7]. Of note, PM-1002 (VB2; K\({}_{11}\)H[(VO)\({}_{3}\)(SbW\({}_{9}\)O\({}_{33}\))\({}_{2}\)]\({}_{2}\)27H\({}_{2}\)O) and PM-19 (K\({}_{7}\) [PTi\({}_{2}\) W\({}_{10}\) O\({}_{40}\)] 6H\({}_{2}\)O) were effective against RNA and DNA viruses, respectively [6; 7; 8]. Additionally, the synergistic effects of PMs combined with oxacillin on MRSA have been demonstrated [9]. In addition, antibacterial/antiviral mixtures were developed by adding antibiotic oxacillin and antibacterial agent Irgasan to three PMs [10,11]. However, its marketing was prohibited in the United States because oxacillin and Irgasan may cause resistant strains. Therefore, oxacillin and Irgasan were replaced by PHMB, and the antiviral activities of minimal formulations (VB2, VB3, and PHMB) were evaluated. The two PM compounds, VB2 and VB3, are the major components for exerting antiviral efficacy, with low cytotoxicity (VB2: IC\({}_{50}\) > 200 M) and a broad viral spectrum (particularly RNA-based viruses) [8,10]. The stability study of the PM solution also showed no change in conformation at 50 \({}^{\circ}\)C for 12 weeks [10].  
In the present study, the effects of a new version of VB on infected cells, hygiene products (in solutions), and solids (materials for stationery items) are investigated. Plaque and TCID50 assays are routinely employed to measure viral titers. However, to establish an evaluation assay free of infectivity and biohazard in culture equipment, RT-PCR was performed with bacterial and viral RNA sequences, and its correlation with TCID50 was examined. In addition, an affinity assay was performed using Biacore X (Biacore, Uppsala, Sweden) because the affinities between virus particles and active compounds may be reflected in antiviral activities [12].  
The antiviral effects of the new version VB were demonstrated on cultured cells and maintained even in hygiene products and solids. RT-PCR for detecting RNA from viruses (e.g., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and norovirus) and bacteria (e.g., MRSA) was established, demonstrating the high affinity of the new version VB for the viral and bacterial components. The application of the VB compound to living environments may have preventive effects on infections.