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A vaccination is the administration of a vaccine, or antigenic. Antigens are substances that, when introduced into the body, trigger the immune system to produce antibodies that kill or neutralize the antigen because it is seen as a foreign threat. Through the administration of vaccines, the likelihood of contracting certain diseases or infections can be greatly reduced. In fact, vaccinations are considered to be the most effective ways of preventing the spread of infectious diseases.Vaccinations have been performed on humans since the 1700s. It is likely that smallpox was the first disease people tried to prevent through vaccination. Using fluid taken from mild cases of smallpox, people were able to reduce their chances of contracting a deadlier strain of the disease. Since the first use of vaccinations, the practice has been met with some controversy on religious, scientific, safety, and ethical grounds. Despite many cases of opposition, however, vaccinations are widely accepted and have been proven to prevent numerous infectious diseases.

How Vaccinations Work

When a vaccine is administered, it primes the immune system with some type of immunogen. Immunization occurs when the immune system is stimulated through the exposure to some type of infectious agent. A vaccine may require the use of one or more immunogens, and they can be administered using different methods and at different times. Most vaccinations are administered directly into the bloodstream with a hypodermic needle, however, some are given orally. Most vaccinations are performed prior to a disease being contracted to prevent it, but in some cases, they may be given after a patient is exposed to an infectious disease.

Types of Vaccinations

All vaccinations prevent the spread of disease by intentionally presenting a foreign antigen to the body to trigger a response from the immune system. There are, however, numerous ways to do this. Presently there are four main types of vaccines that are regularly used. Inactivated vaccines are those that contain virus particles which are grown and then killed. The virus itself is destroyed and cannot reproduce, but it can still be recognized by the immune system. Because the virus cannot replicate, periodic booster shots are required to maintain a patient's immunity. Attenuated vaccinations contain weak live virus particles that reproduce slowly. Virus-like particle vaccines are made using viral proteins that come from an actual virus itself. They can resemble the actual virus and can trigger an immune response, but since they do not have viral nucleic acid, they are not infectious. Lastly, a subunit vaccine is one that presents an antigen without any viral particles. These can be created by producing specific proteins from viruses. Because they do not contain actual viral particles, they often result in weakened immune system responses when compared to other types of vaccines.