Natural infection from certain diseases can kill or seriously harm an individual before the body is able to mount an effective immune response. Vaccines, on the other hand, trigger the body’s natural immune response to produce the necessary antibodies before exposure to the virus. This way, if exposed to the virus, the body has the necessary antibodies to fight off the infection.
Vaccines contain tiny amounts of material that make the immune system produce certain proteins, called “antibodies”, which can attack and destroy viruses and bacteria. The immune system stores the information about how to make these antibodies and later, even many years later, when the body is exposed to that same bacteria or virus, the body “remembers” how to make the antibodies. The body produces the antibodies again, stopping the virus or bacteria from causing illness.
Immunization protects both individuals and the larger population by preventing the spread of infections. Achieving and maintaining a high level of immunization coverage in a population is important in helping to provide the best protection against vaccine-preventable diseases.
Polio has been eliminated in North and South America because most of the population in these continents has been immunized. Many other infectious diseases (such as diphtheria, measles and mumps) are very rare because of vaccination.