Paper/nanomaterial-based sensors,146,147 in general, and, particularly, NP-based lateral-flow devices that are observed with the naked eye or operated through a smartphone are now the most reported testing platforms for the analysis of COVID-19-related biomarkers.148 Nanopaper147 and nanochannels149 may also offer cost-efficient alternatives for detection of viruses and related biomarkers. Nanomaterials are already being used in theranostics applications. Although the field of nanomaterial applications in nanotheranostics is still in its infancy,55 a thoughtful review of the performance characteristics of known nanomaterials may open new avenues of investigation, even for COVID-19-related applications (for both diagnostic and therapies, including vaccines).