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A bacterium, virus, or foreign protein that invades the body is called an antigen. The body senses the foreign antigen and responds by making antibodies. Antibodies are special proteins made by the lymphatic tissue and the reticuloendothelial system; they are designed to help neutralize or resist the effects of invading foreign proteins. In this antigen-antibody response, a specific antigen causes the body to produce an antibody that reacts specifically with that antigen. Some antibodies keep circulating for the life of the person, providing constant active immunity to certain antigens. Other antibodies are active for only a short period, providing passive immunity.

The antigen-antibody response results in immunity, or resistance to invading proteins and diseases. One way a person can develop immunity is by having a disease and recovering from it. An example is when a child develops chickenpox, and the body develops antibodies to the chickenpox virus. These antibodies travel around in the bloodstream for the rest of the person’s lifetime, providing naturally acquired active immunity.

The lymphoid tissue and the reticuloendothelial system tissues will also produce antibodies to a live but weakened antigen (known as a live, attenuated antigen) or an antigen that has been killed. Laboratories can produce vaccines that contain either attenuated or killed antigens, and people can be immunized to prevent them from getting some diseases. This is called artificially acquired active immunity. Whether a weak or dead antigen is given depends on the disease and on what the research has shown is the best way to protect patients. Rubeola (measles) vaccine is an example of a vaccine made from live, attenuated measles antigen. A person who is vaccinated against measles develops a very mild case of measles. The immune system then produces antibodies that protect the person from getting a full infection with measles. Some diseases may require periodic booster injections of vaccine to keep the antibody level high enough to protect the patient from disease.

Some disease-causing proteins that come from invading bacteria are called toxins. Toxins act like antigens to stimulate the immune system to produce antitoxins, which act to neutralize the toxins in the same way antibodies neutralize antigens. When a toxin is attenuated, or weakened, it is called a toxoid. A toxoid can be used to produce immunity because the body cannot distinguish between the toxin and the toxoid. The most common example is the use of tetanus toxoid to protect patients from Clostridium tetani.

Once a person has had an antigen-antibody response, the antibodies are stored in the body. Immune globulins are specific types of protein antibodies that are stored in blood serum and plasma. Concentrated immune globulins are also called antiserums; they may be collected from human or animal sources. A common example is the hepatitis B immune globulin. These antibodies can be injected into a person who does not have immunity to the antigen. The antibodies then circulate to immediately protect this person, but the protection lasts for only a short time. This form of protection is called artificially acquired passive immunity. A type of temporary immunity can also occur when antibodies pass from the mother to the fetus through the placenta or to the nursing infant through breast milk. This is known as naturally acquired passive immunity.

Infants and children can be immunized against diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type B, polio, measles, mumps, rubella, and varicella. These primary immunizations dramatically reduce the incidence of disease in a community and lower mortality and morbidity rates from diseases that were once fatal to many young children. Although most children in the United States have been immunized by the time they enter school, the United States lags behind many other countries in the percentage of children immunized at an early age. Children who are homeschooled often are not immunized. Thus these diseases continue to be widespread and to do damage, particularly when young children bring infections home to older individuals whose immunity may be impaired. We now know that some early immunizations lose their ability to provide long-term immunity. Thus some adults who were vaccinated when they were children may develop pertussis or other diseases to which they believed they were immune. Widespread failure of diphtheria-pertussis-tetanus immunizations led to high rates of pertussis in California recently and guidelines now suggest that all health care providers have pertussis booster immunizations to increase their own immunity.

Every year different immunizations are offered for seasonal flu. As epidemics develop for particular diseases, such as H1N1 influenza, a limited number of immunizations are available. Health care workers should take advantage of these immunizations to protect themselves and to limit exposing their families to these organisms.

Two widespread fallacies have led to the lowered rate of immunizations for children. The first is that immunizations should be withheld if the child is sick. In most cases, a child should be immunized even if they have a mild upper respiratory tract infection or other infection. The second is the fear created by the idea that vaccine immunization in children is linked to the development of autism. There have been no reputable scientific studies to suggest this connection. Licensed practical and vocational nurses should immunize their own children and educate those around them that the risks to children not being immunized is greater than getting an immunization.

Uses

Vaccines and toxoids are the biologic agents used in the routine schedule of active immunizations for adults and children. Specific biologic agents are reserved for use in people who live in areas where specific diseases (e.g., yellow fever, cholera, typhoid) are endemic (common in the community), and there is a high risk of infection. Other vaccines (e.g., pneumococcal vaccine, influenza vaccine) are recommended for people at high risk for specific diseases such as pneumonia or flu.

An additional group of biologic agents (e.g., purified protein derivative [PPD], histoplasmin, coccidioidin) is used in screening procedures to identify people who have been exposed to a specific disease or who may have an active disease such as tuberculosis.

In special circumstances, certain biologic agents (e.g., gamma globulins) may be useful to modify a disease process in the previously unimmunized person.

Adverse Reactions

In general, mild adverse effects of vaccines and other immune agents are common and include localized pain and swelling that are typically mild and of short duration. Claims that immunizations are linked to other health problems have not been supported by scientific studies and data. Although it is true there are rare instances of more serious problems, the risk of complications from the disease far outweighs the risk of adverse effects for all biologic products. Adverse effects occasionally seen include altered levels of consciousness, headaches, lethargy (sleepiness), rash, urticaria (hives), vesiculation (blistering), diarrhea, increased respiratory rate, shortness of breath, arthralgia (joint pain), fever, lymphadenopathy, and malaise (weakness).

Most states have laws requiring infants and children to be properly immunized before starting school. To reduce the liability faced by pharmaceutical companies, a special fund, the National Vaccine Injury Compensation Program, has been established by the federal government to reimburse medical costs incurred if a patient has a serious adverse effect from required immunizations. A certain percentage of the fee paid by the patient for each immunization goes toward this fund, which is administered by the Public Health Service, a division of the U.S. Department of Health and Human Services.

Nursing Implications and Patient Teaching