Tonix Pharmaceuticals Holding Corp. is looking to lessons from tuberculosis and smallpox to guide its future in infectious diseases. The company is developing an intradermal skin test like that used for TB to measure T-cell immunity to SARS-CoV-2, the virus that causes COVID-19. It also has three vaccines in development for COVID-19 that rely on horsepox, likely the form of vaccinia used by Edward Jenner to create the smallpox vaccine.