A vaccine is a biological preparation that provides active acquired immunity to a particular disease. Vaccination is one of the most effective ways to prevent infections. A vaccine helps the body's immune system to recognize and fight pathogens like viruses or bacteria, which then keeps us safe from the diseases they cause. Vaccines are made using the disease-causing virus or bacteria, but in a form that will not harm the human body. Instead, the weakened, killed, or partial virus or bacteria prompts the human body's immune system to develop antibodies, or defenders, against the disease. Vaccines protect against more than 25 debilitating or life-threatening diseases, including measles, polio, tetanus, diphtheria, meningitis, influenza, tetanus, typhoid, and cervical cancer. Vaccines are generally prepared by five major technologies, i.e., conjugate vaccines, live attenuated vaccines, toxoid vaccines, inactivated and subunit vaccines, and recombinant vaccines.