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Pediatric immunization update 2002. (Updates & Kidbits).

Article Excerpt
Changes are made annually to the immunization schedule for children. This is due to continuing growth in the field of immunology and the desire to protect our children from potentially devastating diseases. Usually, new immunizations are developed that enable health care providers to prevent infectious diseases, but occasionally, diseases are eradicated, so a certain immunization schedule may no longer be necessary.

The goal of any immunization program is to protect the population from disease and decrease the incidence of disease and disease transmission. This is done on a scheduled basis by providing immunizations to the population at risk. The purpose of this article is to review the principles of vaccination and the vaccine-preventable diseases, discuss the 2002 recommended pediatric vaccine schedule, overview future trends in pediatric immunizations, and provide current resources.

Principles of Vaccination

Immunology. Immunity is partially defined as protection from an infectious disease (Centers for Disease Control and Prevention [CDC], 2000a). The purpose of the immune system is to identify unknown (non-self) substances in the body and develop a defense against these invaders. Immunity can be provided either passively or actively.

Passive immunity is protection transferred via already formed antibodies from one person or animal to another. Passive immunity includes transplacental passage of antibodies from a mother to her infant, immunity provided through breast milk, and immunity from administration of immunogiobulins (human or animal). Passive immunity provides protection for a limited time period and then decreases over a period of weeks or months (CDC, 2000a).

Active immunity is protection produced by a person's own immune system. Active immunity includes an immunologic response to a modified antigen (as in many of the vaccinations) or immunity gained from actual infection by contracting the disease. Active immunity may be lifelong once a complete series of immunizations is administered (CDC, 2000a).

Classification of vaccines. Administration of vaccinations is an attempt to stimulate immunity in a person by administering either a live attenuated vaccine or an inactivated one. A live attenuated vaccine uses a live organism, attenuated (modified) in the lab. Once attenuated, this organism retains the ability to replicate and stimulate immunity. Attenuated live viruses or bacteria mimic the natural infection and may produce long lasting immunity with just one dose, although a series is needed to develop a protective titer (Humiston & Strikas, 2001). Adverse effects seen after vaccination with live vaccine are similar to those seen with a mild form of the actual illness. Measles, mumps, and rubella (MMR), oral polio vaccine (OPV), and varicella vaccine (VZV) are common examples of live vaccines.

An inactivated vaccine is created from bacteria or viruses grown in a culture media, purified, chemically modified, then inactivated or "killed;" it is capable of producing an immune response, although less than with the attenuated vaccines. The inactivated vaccine cannot cause the disease in the recipient, yet it can provide partial immunity. An inactivated vaccine is generally less effective and may require multiple doses and periodic boosters to maintain immunity. A booster is the administration of at least one additional dose of the vaccine to raise the recipient's antibodies back to protective levels (CDC, 2000a). Adverse effects from inactivated vaccines are usually local reactions to the vaccine, such as redness, tenderness, or swelling at the injection site. Diphtheria, tetanus, and acellular pertussis (DTaP), inactivated polio vaccine (IPV), Hepatitis B (HBV), Hepatitis A (HAV), haemophilus infiuenzae type B (Hib), and pneumococcal conjugate vaccine (PCV7) are examples of inactivated vaccines. Inactivated vaccines are further classified as whole cell vaccines or fractional vaccines.

Inactivated vaccines can be composed of either whole viruses or bacteria or fractions of either. Fractional vaccines are those in which the inactivated bacteria or virus is further treated to purify only those components to be included in the vaccine (CDC, 2000a). Examples of fractional vaccines include toxoids (toxins treated so as to destroy their toxicity, yet still capable of inducing formation of antibodies on injection), pure polysaccharide vaccines, and conjugated polysaccharide vaccines. The conjugation process (used in the Hib and PCV7 vaccines) changes the recipient's immune response leading to increased immunogenicity and antibody booster response (CDC, 2000a).

Vaccine-Preventable Diseases

The Advisory Committee on Immunization Practices (ACIP), the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP) recommend which immunizations should be given to children to protect them from acquiring communicable diseases that have a high rate of morbidity (see Figure 1). Table 1 contains a list of childhood diseases that are vaccine-preventable along with their incubation periods, signs and symptoms, periods of communicability, transmission, and proper precautions.

Standard precautions. Standard precautions used to be called universal precautions. Standard precautions include good handwashing, avoiding contact with any body fluids or potentially infectious materials, and using personal protective equipment, such as gloves, gowns, masks, and goggles as appropriate (AAP, 2000a). To avoid contact with body fluids, standard precautions should be used when caring for any patient.

Transmission-based precautions. Transmission-based precautions are used when needed for specific patients who may be infected with certain pathogens that require additional precautions to prevent the transmission of the disease. Transmission-based precautions should always be used in addition to standard precautions. The three types of transmission-based precautions are airborne, droplet, and contact.

Airborne precautions are used if the illness or disease can be spread to others through the air (AAP, 2000a). These small particle droplets can remain suspended in the air for long periods of time and may be spread via air currents. Therefore, the microorganisms can be inhaled throughout the room or at a long distance from the patient. This necessitates wearing a particulate respirator mask and having the patient in a negative-flow room that vents to the outside to prevent transmitting the disease throughout the hospital or clinic.

Droplet precautions are used if the illness or disease can be spread through large droplets of saliva when coughing, sneezing, or talking (AAP, 2000a). These droplets generally do not remain suspended in the air and usually spread to those within three feet of the patient. Droplet precautions require wearing a mask if within three feet of the patient.

Contact precautions are used when the illness or disease can be spread by touch or direct personal contact (AAP, 2000a). Gloves and gowns should be worn when caring for these patients.

Why Are Immunizations Important?

What should one say when parents ask why their child should receive all of these immunizations? Failure to immunize is important not only to the individual child, but it also has societal and global implications for limiting the spread of disease. According to epidemiologic data, there has been a sharp decline in disease incidence following licensure and use of each new vaccine (National Association of Pediatric Nurse Associates and Practitioners [NAPNAP], 2000). it is critical that health care providers know and understand the incidence and sequelae associated with these vaccine-preventable diseases and are able to discuss the benefits and risks with parents.

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