The body's immune system is responsible for protection against pathogens—bacteria, viruses, and other microorganisms—that cause infection. Most of the time, the immune system—made up of special cells, tissues, and organs—is efficient at either keeping foreign invaders out or tracking them down and eliminating them inside the body. However, some pathogens, especially ones the body does not recognize, can overwhelm the immune system and cause major problems. Vaccination is a way to "teach" the immune system how to recognize and eliminate an organism, should it find its way inside the body.
Experts point to vaccines as a major source of primary prevention that can protect people from getting sick in the first place. In recent years, opponents of vaccinations challenge the safety and effectiveness and have attempted to erroneously link vaccines as a potential cause of other conditions, such as autism. However, diseases that once threatened newborns and children—measles, whooping cough—have been significantly controlled through vaccines.
Despite this progress, evidence shows that a staggering number of people don't get vaccines simply because they don't know about them. Each winter season, we're encouraged to get our flu vaccine. Yet, national polls between 2005 and 2010 reveal that 60 percent of Americans did not get the annual flu shot. Not getting vaccinated puts people at risk for developing infectious diseases; it can also lead to costly doctor's visits and hospital fees.
What is Immunity?
A healthy immune system knows its role as a defender against invaders. The immune system is composed of several types of cells that can defend against, neutralize, and remove harmful pathogens from the body. Immunization involves the processes of stimulating antibodies to remember harmful antigens and of priming specific cells to develop a memory for infections.
Vaccines work by giving the immune system copies of a partial protein, whole protein, polysaccharide, or weakened or neutralized pathogen. The immune system subsequently responds to this invader and builds an adaptive response to increase the likelihood that, should the actual disease present itself, the body will be equipped to fight it off. Usually administered by injection (but sometimes in a pill form), vaccines exploit the immune system's incredible ability to recognize and remember foreign invaders.
Active vs. Passive Immunity
Active immunity is the body's long-term, adaptive way of remembering a pathogen and recognizing it as a foreign invader. This is either through having experienced the pathogen in nature and built-up resistance (natural immunity) or through a vaccination (artificial immunity).
Passive immunity is the short-term transfer or administration of active immunity to a person. This can also happen naturally, such as from mother to child through childbirth, or artificially through the injection of immune globulin (antibody-containing blood products).
What if We Stopped Vaccinations?
Vaccines can reduce—or even eliminate—disease. Efforts to eliminate polio led to the disease's demise in the Western hemisphere. According to the Centers for Disease Control and Prevention (CDC): "Before the polio vaccine was available, 13,000 to 20,000 cases of paralytic polio were reported each year in the United States." Similarly, measles once afflicted large numbers of people in the United States. Vaccination "led to a greater than 99 percent reduction in measles compared with the pre-vaccine era," according to the CDC.
Ending vaccination would introduce a host of complications from the spread of pathogens. The World Health Organization (WHO) continues to work—through research, vaccine safety, and vaccine regulations—in order to prevent the millions of deaths that occur due to preventable diseases. The WHO estimates that, worldwide, "over one million infants and young children die every year from pneumococcal disease and rotavirus diarrhea"—a significant number of which could be prevented through immunization.