Know about vaccine

Vaccines are whole or parts of microorganisms given to prevent an infectious disease. Vaccines can consist of whole inactivated microorganisms, parts of organism like polysaccharide capsules, live attenuated microorganisms and toxoids. A toxoid is a modified bacterial toxins that is made nontoxic but is still able to induce an active immune response against the toxin. All vaccines are subjected to three phases of clinical trials. Phase I involves generally less than 100 participants mainly to gauge safely and dosing. Phase II involves several hundred or more participants to refine safely and dosing; and finally phase III that involves thousands of participants. Phase III trials are the major basis for licensure.