Patient information: Childhood immunizations

CHILDHOOD IMMUNIZATIONS OVERVIEW

Immunizations are one of the most effective ways to prevent serious illness in children and adults. Pediatric immunization programs in the United States have been quite successful in reducing the number of children affected by a range of highly contagious diseases, including measles, rubella, mumps, diphtheria, and poliomyelitis.

The following is a discussion of how immunizations work, common side effects, reasons to avoid a particular vaccine, and common concerns about immunizations. Separate articles discuss individual vaccines. (For children: (see "Patient information: Immunizations for infants and children age 0 to 6 years" and "Patient information: Immunizations for children age 7 to 18 years") and for adults: (see "Patient information: Adult immunizations".

HOW DO IMMUNIZATIONS WORK?

The immune system functions to protect the body against illness and infection. When an organism (bacterium or virus) is foreign to the body, the immune system detects the organism and responds by creating proteins called antibodies. Antibodies fight the infection and help the person to recover.

Antibodies also work to prevent a person from becoming ill in the future. If a person is exposed to the organism again, the immune system recognizes it and rapidly produces more of the antibodies required to destroy the organism. This response protects the individual from developing the disease, ideally for life. For example, a person who had chickenpox as a child is unlikely to develop it again, even if he or she is in close contact with a person who is infected.

Vaccines work by stimulating the immune system to produce antibodies. However, unlike bacteria and viruses, vaccines do not cause the person to become ill in order to develop these antibodies. There are two main types of immunizations: active and passive.

Active immunization — Active immunizations use a weakened form of the harmful bacteria or virus or components of the bacteria or virus to stimulate the immune system. Some vaccines used for active immunization are called live attenuated vaccines because they are made from a weakened form of the bacterium or virus.

Some bacteria (eg, diphtheria, tetanus) cause illness because they produce harmful substances called toxins. Vaccines that help the immune system protect the body from toxins are called toxoids. Toxoids are made from weakened forms of the bacterial toxins.

Passive immunization — Passive immunizations provide temporary immunity using antibodies obtained from a large pool of donors; this type of preparation is known as immune serum globulin. Passive immunization offers short-term protection to children or adults who have been exposed to a specific organism.

One example of passive immunization is hepatitis B immune globulin (HBIG). HBIG is given to newborns whose mothers test positive for hepatitis B surface antigen (HBsAg). HBIG provides temporary protection to the newborn against infection with hepatitis B.

Immunizations protect children and adults — Many parents are concerned about the risks of vaccination. However, vaccines have a long record of being a safe and effective way of preventing disease. In most cases, the benefits of immunizing a child are far greater than the potential risks.

Diseases such as diphtheria and measles were common at one time in the United States, but are no longer a significant threat because of immunization programs. However, these illnesses are still common in developing countries throughout the world. Because it is easy to travel from one country to another, it is easy for illness to spread from children or adults who are not vaccinated. Immunization helps to reduce a child's, family's, and even an entire community's chances of becoming ill by decreasing the number of people who get sick and transmit the infection to others. This process is sometimes referred to as "herd immunity."

An example of a successful immunization effort is the smallpox immunization program. Before a vaccine was available, smallpox killed millions of people every year. Up until the early 1970s, smallpox disease was a worldwide threat to life. Use of the smallpox vaccine in large populations of people prior to the 1970s led to complete eradication of the disease and the smallpox vaccination is no longer required.

How are immunizations given? — In children, most immunizations are given in the form of an injection. For children younger than two years, most injections are given into the thigh. For older children or teenagers, the injection may be given into the thigh or the upper arm. Some immunizations are injected into the skin (called subcutaneous injections) while others are injected into the muscle (called intramuscular injections). Vaccines are also given in other ways, such as in a liquid taken by mouth (eg, rotavirus) or as a nasal spray (eg, one form of the influenza vaccine).

Paying for vaccines — Vaccines are available for every child in the United States, even for those who do not have health insurance. If a child does not have health insurance and the parents are unable to pay for vaccines, a program called Vaccines for Children is available. This program helps to cover the costs of vaccines given at private doctor's offices, clinics, hospitals, community health clinics, and in some schools (www.cdc.gov/nip/vfc/).

IMMUNIZATION SIDE EFFECTS

Most vaccines and toxoids are safe and cause few if any serious side effects. Very rarely, serious side effects do occur. Children who develop unusual reactions such as rashes involving much of the body surface, difficulty breathing, excessively high fevers, seizures or loss of consciousness within a short time after receiving a vaccine should be evaluated by a healthcare provider. To report an unusual reaction after a vaccine, anyone can contact the national Vaccine Adverse Events Reporting System (VAERS, www.vaers.org, telephone number 1-800-822-7967). Parents who are concerned about a particular vaccine should discuss their concerns with their child's healthcare provider.

Mild side effects — Vaccines and toxoids can occasionally cause mild side effects, including:

• A low-grade fever
• A red and tender area at the site of an injection

Moderate side effects — Occasionally, children can develop a combination of fever, skin rash, swollen lymph nodes, and/or joint pain after vaccination. These reactions, called serum sickness-like reactions, can be uncomfortable, although they are rarely dangerous and resolve without treatment in days to weeks.

Severe side effects — Severe side effects of vaccines are rare, but may include a severe neurologic reaction (eg, seizures) or severe allergic reactions (eg, anaphylaxis). Allergic reactions usually occur within minutes to hours of receiving the vaccine. If this occurs in the healthcare provider's office, emergency care can be given immediately. If a severe reaction occurs later, the parent/guardian should call emergency medical services, available in most areas of the United States by calling 911.

Reasons to avoid vaccination — A particular vaccination may not be recommended for children with a serious allergic reaction to the following (table 1):

• Eggs or egg protein, since some vaccines are prepared with embryonic chicken eggs or cultures (eg, influenza vaccines, yellow fever vaccines, (table 2). A mild allergic reaction to eggs does not mean that the vaccine should be avoided.
• The antibiotic medications neomycin or streptomycin (some vaccines contains trace amounts of neomycin)
• Gelatin (table 3)

• A specific vaccine in the past

In some cases, parents may not know their child is allergic to one of these components until the vaccine is given and the child develops a reaction.

In addition, live virus vaccines are generally not recommended for children with a weakened immune system since there is an increased risk of infection as a result of the vaccine. However, there may be exceptions to this recommendation.

Immunization with MMR and varicella vaccine should be delayed in children who have recently received a blood transfusion or blood products (eg, immunoglobulin preparations) since these products can make the vaccine less effective.

Conditions that do not affect vaccination — The following conditions do not require delaying or avoiding immunization:

• Current or recent mild illness
• Current or recent antibiotic therapy
• Previous mild to moderate tenderness, redness, or swelling at the site of injection or fever less than 104.9ºF (40.5ºC) after a previous vaccination
• A personal history of allergies, except those listed above
• A family history of adverse reactions to immunization

Concerns about vaccination — There have been concerns within the general public about the safety of vaccination for children. These concerns include use of the preservative thimerosal and the relationship between vaccines and autism.

Thimerosal is a derivative of mercury that was previously used as a preservative in most vaccines. As the number of vaccinations given to infants increased, there was concern that this preservative could lead to potentially unsafe levels of mercury levels in some infants. As a result, several expert groups recommended in 1999 that all standard childhood vaccines be produced without thimerosal. The recommendation was a precautionary change and was not based upon known harm from thimerosal. Thimerosal-free forms of all of the childhood vaccines are available in the United States.

A second concern was in regards to a possible relationship between certain vaccines and the subsequent development of autism. Despite this concern, there is no scientific evidence that receiving these vaccines causes or increases the risk of developing autism. Studies that raised this possibility had significant weaknesses in their design. Several of the studies were based on a small number of children and relied upon the memory of parents or pediatricians to recall when behavioral signs/symptoms related to autism began. Most studies did not include a control group to compare children who were vaccinated with those who were not vaccinated to determine if there was a cause and effect relationship. It was recently reported that some cases of autism are attributable to gene abnormalities. For more information about any potential link between vaccines and autism, visit the National Immunization Program Web site at www.cdc.gov/vaccines.

IMMUNIZATIONS RECOMMENDATIONS

Children should begin receiving vaccines within the first few months of life. This allows the child to be protected from common childhood illnesses as well as illnesses that can develop during adulthood. Many diseases prevented by vaccines are more serious in young children. In addition, most infants visit a healthcare provider frequently during the first year, which improves the chances of completing most vaccines that require multiple doses. In most states, specific vaccines are required before the child can attend school. This policy is designed to not only protect the individual child but to prevent the spread of certain contagious diseases to other children attending the school; these requirements vary from one state to another.

In the United States, certain vaccines are recommended for children between birth and 6 years. These include vaccines against hepatitis A and B, diphtheria, tetanus, pertussis, Haemophilus influenza B, polio, measles, mumps, rubella, varicella-zoster virus (VZV), pneumococcus, influenza, and rotavirus (graph 1). The use of combination vaccines can help to reduce the number of injections at each visit. (See "Patient information: Immunizations for infants and children age 0 to 6 years".)

The timing of vaccines is important; some vaccines are most effective when given to children at a particular age or in combination with other vaccines. A personal, customized immunization schedule can be created at the CDC's National Immunization Program Web site (www2a.cdc.gov/nip/scheduler_le/default.asp). The schedule may be helpful in reminding parents when their child is due for vaccines.

The CDC has also developed an online tool for children younger than six years to help determine which immunizations have been missed and when the vaccines should be scheduled (www.cdc.gov/vaccines/recs/Scheduler/catchup.htm).

WHERE TO GET MORE INFORMATION

Your child's healthcare provider is the best source of information for questions and concerns related to your child's medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your child's situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Immunizations for infants and children age 0 to 6 years
Patient information: Immunizations for children age 7 to 18 years
Patient information: Adult immunizations

Professional Level Information:
Allergic reactions to vaccines
Clinical trials of human papillomavirus vaccines
Epidemiology, clinical manifestations, diagnosis and management of mumps
Hepatitis A virus vaccination and postexposure prophylaxis
Hepatitis B virus vaccination
Impact of universal infant immunization with pneumococcal (Streptococcus pneumoniae) conjugate vaccines in the United States
Meningococcal vaccines
Pneumococcal (Streptococcus pneumoniae) conjugate vaccines in children
Poliovirus vaccination
Prevention of varicella-zoster virus infection: Chickenpox
Recommendations for the use of human papillomavirus vaccines
Rubella
Seasonal influenza vaccination in children
Standard childhood immunizations
Treatment of varicella-zoster virus infection: Chickenpox
Vaccinia virus as the smallpox vaccine

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• National Institute of Allergy and Infectious Diseases

      (www.niaid.nih.gov/)

• Centers for Disease Control and Prevention (CDC) National Immunization Program

      Toll-free: (800) 311-3435
      (www.cdc.gov/nip/default.htm)

• National Foundation for Infectious Diseases

      Tel: (301) 656-0003
      (www.nfid.org)

• The Children's Hospital of Philadelphia Vaccine Education Center

      (www.chop.edu/consumer/jsp/microsite/microsite.jsp?id=75918)

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