What Is Vaccination and Why Is It Used?

The administration of vaccines is called vaccination. Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the restriction of diseases such as polio, measles, and tetanus from much of the world.

The effectiveness of vaccination has been widely studied and verified; for example, vaccines that have proven effective include the influenza vaccine, the HPV vaccine, and the chicken pox vaccine. The World Health Organization (WHO) reports that licensed vaccines are currently available for twenty-five different preventable infections.

Over time, scientists have developed several methods for creating effective vaccines. Let’s take a closer look at some of the most popular methods. The MMR (measles, mumps, and rubella), chickenpox, and shingles vaccines are all made using weakened viruses. By weakening the viruses that cause these diseases, scientists ensure that they reproduce poorly when injected into the body in the form of a vaccine.

A full-strength virus can reproduce thousands of times over the course of an infection. A weakened virus, however, usually reproduces fewer than 20 times. The result is that weakened viruses don’t produce disease, but they reproduce enough for the body to build up a resistance and even produce memory cells that will continue to fight the virus in the future.

Weakened-virus vaccines usually produce lifelong immunity with only one or two doses. The downside to these types of vaccines is that they usually can’t be given to people with weakened immune systems.

Influenza, rabies, hepatitis A, and polio vaccines are made using completely inactivated viruses. Since the virus has been killed chemically, it can’t cause disease, but it can still be recognized by the body in order to produce immunity.

Inactivated-virus vaccines can be given to people with weakened immune systems. However, these types of vaccines usually require several doses to achieve immunity.

Many other types of vaccines are made by using only one part of a virus or bacterium. For example, a particular protein or toxin associated with a virus or bacterium can be inactivated and used to create a vaccine that can be given to people with weakened immunity in order to achieve lifelong immunity with as few as three doses.

As diseases evolve, scientists continue to look for ways to create vaccines to protect people from harm. Some people also experience decreased immunity over time. When this occurs, vaccines called “boosters” can be given to restore full immunity. This happens frequently with vaccines for tetanus, for example.

Content for this question contributed by Clara Wright, resident of Pomona, Los Angeles County, California, USA