Vaccine

From ArticleWorld

A vaccine, which is a very complex solution, is used to prevent an infection, or at least to ameliorate its effects, allowing the immune system of the body to fight the infection more easily.

The vaccine got its name from vaccinia, the Latin term denoting the pathogen agent that causes cowpox. This is not surprising, as the smallpox is one of the first disease people tried to prevent by vaccination.

Historically, the first vaccines seemed to be used by the Indians, who would purposely inoculated healthy people with agents causing a mild case of smallpox, using bits of the drying pustules. Similar practices were reported, in time in Turkey and China, while Europeans would use fluids infected with the cowpox virus.

In time, various other ways of developing vaccines were discovered, including techniques to allow mass multiplication of doses.

Types

Vaccines induce immunity by various techniques. Depending on what type of agents they use to induce this immunity, we can find a number of vaccines.

• Inactivated: these vaccines contain dead virulent agents. The vaccines against flu and hepatitis A are the most common examples.

• Live, but attenuated: these vaccines contain living agents, grown under certain conditions. This causes them to lose their virulent function, while providing a long-lasting immunity for the host. The vaccine against yellow fever is such a vaccine.

• Toxoids: these vaccines use inactivated toxic components that cause the diseases. They are used against the diseases where the agents themselves don't cause any harm, but the substances they synthesize or summon by some other ways do.

Some innovative techniques have appeared in time, like those involving conjugate vaccines or DNA vaccination.

Immunity

The human organism develops immunity to the agents inoculated by vaccine by destroying them first, and then remembering how to create antibodies. When an active, full-blown agent enters the organism, the immune system will be able to recognize and destroy the agent before it enter the cells, or destroy the cells if they become infected.

Vaccines also create what is known as herd immunity. When the vast majority of the population has been vaccinated against a disease, powerful outbreaks are less likely to occur.