According to the Merriam-Webster dictionary, a vaccine is defined as a preparation of killed microorganisms, or living, virulent organisms, that is administered to produce or artificially increase immunity to a particular illness. There are approximately fifty major vaccines used in the United States to prevent bacterial and viral diseases in humans. Disease prevention is a primary public health concern in the United States Over the past two centuries, vaccines have successfully prevented numerous cases of infectious diseases including: polio, measles, diphtheria, whooping cough (whooping cough), rubella (German measles) , mumps and tetanus. In fact, it was a vaccine that eradicated smallpox, one of the most harmful diseases, in 1977. The immune system plays a fundamental role in the fight against infectious diseases. It can identify pathogens that enter the body as foreign “invaders,” or antigens. This, in turn, signals the production of large Y-shaped proteins called immunoglobulins (antibodies), which are used to detect and neutralize these foreign substances. Vaccines contain the same antigens that cause disease; however, they are attenuated so that they are not strong enough to cause disease, but are able to stimulate the immune system to produce antibodies against them. In essence, vaccination protects against disease by triggering the immune response against a specific pathogen. Through vaccination, people are able to develop immunity without suffering from the actual diseases prevented by vaccines. Herd immunity is described as the resistance of a population to infection and the spread of an infectious organism due to the immunity of a large percentage of a population. The level... in the center of the card... faces. This is because, during transmission, HPV targets proliferating epithelial cells. Once inside the epithelial cell, the viral genome begins to replicate. Subsequently, the released HPV particles are able to infect a new host and the process repeats. The “high risk” potential of the HPV type is mediated primarily by virulence factors that include the E6 and E7 proteins. These proteins have been shown to bind to and degrade the tumor suppressor protein p53 and retinoblastoma protein (Rb), leading to inhibition of gene expression of normal cell division. Inactivation of p53 affects cell apoptosis at the G0 checkpoint and causes cell cycle arrest. When E7 binds to Rb, the Rb-E7 complex is degraded and cells proceed to divide at an unregulated rate. This uncontrolled division is responsible for the malignant cells present in cervical cancer.