Immunizations are a series of shots that provide basic protection against certain diseases. The vaccines used in this process contain tiny amounts of the disease – either in killed or weakened form – that are injected into the body. The immune system perceives these injected microorganisms as a threat and responds by creating antibodies to the disease.

Antibodies recognize specific parts of a germ and attack it. Once these antibodies have been created, they are ready to protect the child on any future occasions when the child is exposed to an actual live form of the virus or bacteria. This process is known as developing immunity.

The microorganisms used in vaccines to create antibodies typically are either viruses (e.g., measles) or bacteria (e.g., pneumococcus). In some cases, an organism’s identifying protein or carbohydrate is used. In the past, these vaccines sometimes were delivered through oral solutions, but today they all are given through injections. In addition, there is an increasing tendency to combine vaccines in a single injection.

Young children receive most immunizations, both because many diseases are most prevalent in early childhood and because the immune systems of young children are still developing and may need an extra boost. Most U.S. states require that children receive certain vaccinations before they are allowed to attend daycare, school or camp. However, these vaccines should be given early in life because younger children are more vulnerable to the effects of these infections, which also tend to be more prevalent in younger children.

Immunizations have dramatically reduced the incidence levels of certain childhood diseases. Diseases such as polio, measles, diphtheria, pertussis (“whooping cough”) and tetanus once killed hundreds of thousands of people every year, but now pose very little thereat to people in the United States and most of the Western industrialized world. In the case of smallpox, immunizations have helped to actually eliminate the disease worldwide.

Immunizations can also be used to treat diseases that are contagious, but not life-threatening. These include rubella, chickenpox and mumps. Although these diseases rarely result in fatalities, they may cause complications ranging from hearing loss to sterility (inability to procreate).

Because many diseases have now become uncommon, some parents may no longer feel a sense of urgency about immunizations. Some parents also fear their children will experience side effects associated with these vaccines, or that they will acquire the very disease that the vaccine is intended to protect against.

However, most side effects are mild and easily treatable. Speculation of a potential link between vaccines and other disorders (e.g., autism, attention deficit hyperactivity disorder, sudden infant death syndrome, multiple sclerosis) appears to be unfounded, according to numerous studies that have addressed this question. One vaccine preservative, thimerosal, has been removed or reduced to trace amounts in all childhood vaccines except for the influenza vaccine as a precaution against unnecessary toxic exposure. In addition, a child cannot get a disease from most vaccines, which are made with dead bacteria or viruses. Vaccines that consist of weakened viruses – such as those used to protect against chickenpox or measles, mumps and rubella – occasionally pose a small threat of the child contracting the disease, which then occurs in much weakened form.

It is important that all children continue to have immunizations according to a schedule established by medical experts. This protects not only the child, but all people who have contact with the child. Immunization is not necessary only in cases where a disease has been eradicated throughout the world, such as smallpox. Diseases that no longer are present in the United States – such as diphtheria – could still return because they are present in other parts of the world.

In recent years, the incidence of measles in the United States has increased from less than 2,000 cases annually to more than 50,000. Experts believe this is largely because a reduction in the number of measles vaccinations has allowed the virus to regain a foothold in the population. Another disease that appears to be making a comeback in the United States is pertussis (“whooping cough”). The incidence of the whooping cough has increased from about 1,000 cases each year to more than 25,000. Experts believe this is mostly due as a result of adolescents and young adults not receiving the recommended booster shots. 

The Food and Drug Administration (FDA) tests and approves all vaccines for safety. In some cases, these vaccines almost completely protect a child from disease. In other cases, they protect the vast majority of children who are immunized. Children who are vaccinated yet still become infected usually have a milder form of the condition than those who are not immunized.

Following is a schedule for childhood immunizations: