OptiBac daily immunity has been created especially for those looking for natural immune support. It contains the extensively researched strain Lactobacillus paracasei CASEI 431^®, as well as vitamin C which helps to support your body’s resistance to infection and supports a healthy immune system. L. paracasei CASEI 431^® has been studied in numerous clinical trials on thousands of people. This strain is typically studied on its own as a single strain, so we decided to keep it that way.