Immunizations In-Depth

Immunizations against childhood diseases have saved millions of lives. American vaccination rates are now at an all-time high. Disease and death from diphtheria, pertussis, tetanus, measles, mumps, rubella, and Haemophilus influenzae (H. influenzae) type b are at or near record lows. In adults, immunizations against influenza (the flu), pneumococcal pneumonia, hepatitis, and other ailments have likewise saved many lives and prevented many more cases of serious illness.

More than 70 bacteria, viruses, parasites, and other infectious microbes cause major human disease. Fortunately, vaccines are either available or being developed against many of them. With the advent of new or newly feared biological threats, emerging infections, and bacterial resistance to common antibiotics, immunizations are assuming an increasingly important role in maintaining the health of billions of people worldwide.

Immunizations (vaccinations) are given to initiate or augment resistance to an infectious disease. Immunizations provide a specialized form of immunity that provides long-lasting protection against specific antigens, which cause disease.

General Guidelines

Routine Childhood Vaccines. Experts recommend that all children be routinely vaccinated against the following diseases:

• Measles
• Mumps
• Rubella (German measles)
• Diphtheria
• Tetanus
• Pertussis (whooping cough)
• Poliomyelitis (polio)
• Varicella (chickenpox)
• Hepatitis B
• Hepatitis A (recommended in selected states and in certain high-risk populations)
• H. influenzae type B (a cause of meningitis)
• Influenza (children aged 6 - 23 months)
• Pneumococcal disease.
• Meningococcal disease (for selected populations)

Many vaccinations are first given during infancy. Even premature infants can, in most cases, be given vaccinations on a normal schedule. There is even some evidence that doing so may offer some slight protection against sudden infant death syndrome. Note: These facts pertain to children in the United States. Children from other countries have not been well studied. Parents who adopt internationally may want to have their children's immunity assessed by a physician. Some evidence suggests that their medical records may not correctly reflect immunization status and that many adopted children, such as those from China, have not had many important vaccinations.

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Common Adult Vaccines. Vaccinations against the following disorders are also recommended routinely for certain adults:

• Influenza (flu). Every year in high-risk adults under 49 and everyone over 50. When supplies are limited, as with the 2004 - 2005 flu season, the vaccine should be administered preferentially to adults only over age 65 and to individuals with heart disease, lung disease, and other significant chronic illnesses. Health care providers with direct patient contact, child care providers, and residents of long-term care facilities should also be vaccinated.
• Pneumococcal pneumonia. One dose in high risk adults under 64 and a first dose or a revaccination in everyone over 65.
• Hepatitis A and B and Meningococcal vaccine. Given to high-risk individuals.
• Tetanus. Adults need a booster shot every 10 years.
• Measles, mumps, rubella. Typically given to adults under 50 who are unsure of their vaccination history. High-risk individuals may receive two doses.
• Varicella (chickenpox). High-risk individuals may receive two doses.
• Diphtheria and pertussis are now recommended with tetanus (Tdap vaccine) booster every 10 years until age 65.
• Herpes zoster (shingles) vaccine is now approved for adults under age 65. Zostavax is a shingles vaccine approved for adults 60 years of age and older.

Vaccine Forms

Vaccines are currently taken by mouth (orally) or given by a shot (injection). Vaccines are usually made of one of two agents that cause the body to produce antibodies that attack a specific disease. A vaccine may contain:

• A live but weakened virus. Live-virus vaccines provide longer immunity than inactivated ones, but they can cause serious infection in people with weakened immune systems and have also been associated with severe medical disorders in rare instances.
• Inactivated bacteria, viruses, or toxoids. Inactivated vaccines are safe even in people with impaired immune systems.

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The weakened or inactivated agent in the vaccine teaches the immune system to recognize the real, harmful substance and attack it when the person becomes exposed to the infection. The antibodies remain in the body, preventing future illness from the disease. This is called immunity.

Combination Vaccines. The American Academy of Pediatrics and American Academy of Family Physicians recommend that health care providers use, whenever possible, combination vaccines instead of individual components. Currently a child must have 20 injections in the first year of life for full recommended immunity. Combination shots containing vaccines for diphtheria, tetanus, and pertussis (DTaP), and for measles, mumps, and rubella (MMR) have been available for years. New combinations that cover up to five vaccinations are being developed and are proving to be safe and well tolerated in infants as young as t2 months. For example, one that combines DTaP, hepatitis B, and the polio vaccine (Pediarix) has been approved and should simplify the immunization process.

There is some concern that increasing use of combinations may reduce the potency of some of the vaccines within other combinations. Some parents are also worried about increased side effects. Studies, to date, however, are reporting that combinations are effective and safe.

Passive Immunity. Another form of protection against disease is called passive immunity. This approach uses immune globulin, which are blood products containing antibodies. Immune globulin is generally used for people who cannot be vaccinated, when immediate protection is required, or to prevent severe complications of the disease. In some circumstances, passive immunity can interfere with active vaccinations, particularly live-virus vaccines, so, if possible, they should not be administered within weeks or even months of each other.

General Information on Side Effects. Vaccines can have side effects, such as swelling at the injection site or fever, which are nearly always mild. There have been a number of reports in the popular press about alarming side effects in many vaccines. Anti-vaccine groups vocally oppose immunizations in children. Although it is true that no vaccine is 100% safe, childhood infections have not been wiped out. Without immunization, children risk diseases that have in the past killed millions of young children.

Vaccination Recommendations During Pregnancy

Inactivated-virus and toxoid vaccines are usually safe in pregnant women, although any vaccination should be delayed, if possible, until the second or third trimester. Because of a possible risk to the fetus, live-virus vaccines should not be given to pregnant women or those likely to become pregnant within 28 days unless such women need immediate protection against life-threatening diseases, such as yellow fever, that are only prevented using live-virus vaccines. The live-virus MMR combination, which vaccinates against measles, mumps, and rubella, is not given to pregnant women because of the theoretical risk of the live-rubella vaccine on the fetus.

Click the icon to see an image of rubella syndrome.

Vaccination Recommendations for People with Compromised Immune Systems

Live-virus vaccines are not usually given to people whose immune system has been compromised by illness or the use of medication such as long-term corticosteroids. They include:

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• Persons who have immune deficiency diseases (such as HIV or AIDS).
• Patients with active leukemia or lymphoma.
• Patients who are taking treatments that suppress the immune system, such as corticosteroids, alkylating drugs, antimetabolites, or radiation. (There are important exceptions, however, which are noted in the discussion of individual vaccinations below.) Short-term corticosteroids (given for less than 2 weeks) do not suppress the immune system and so should not affect any live-virus vaccination. It should be noted that some topical corticosteroids are suppressive. Patients who need vaccinations and who take long-term or high-dose topical steroids should check with their physicians.

In general, vaccines are not completely effective for patients whose immune systems are compromised by disease or medications. Often, such patients are given immune globulin if they are exposed to infection. Experts estimate that it takes 3 months to 1 year before a person who has stopped taking immunosuppressant drugs regains the full ability to be successfully immunized against disease.

Vaccinations for Travelers to Developing Countries

People who are traveling to developing countries should check with the US Centers for Disease Control (www.cdc.gov/travel) for up-to-date information on immunization requirements for their destination.

Below are some general guidelines for vaccinations, immunizations, and other preventive steps for travel:

• Everyone should be up-to-date in any recommended vaccinations for childhood diseases, regardless of their age. Booster shots may be required for travelers to developing countries even if they have completed the initial series. Vaccinations may include polio, H. influenzae, the series for diphtheria, pertussis and tetanus (DPT), hepatitis B, rotavirus, measles, and varicella-zoster (chickenpox). If children have not completed their DPT series, parents should consider having it completed while overseas.
• Pregnant women should have vaccinations that are appropriate to their trimester. Not all vaccinations are safe during pregnancy.
• Older adults may not respond to a vaccination as quickly as younger people or they may have a higher risk for side effects. They should check with their physicians.
• Upper respiratory infections are very common after foreign travel. The flu vaccine may be recommended when traveling to any country during flu season, particularly for the elderly and people at risk for serious illness. This group may also need the pneumococcal vaccine.
• Travelers to areas where there are tuberculosis (TB) outbreaks should have skin tests before traveling; those with negative tests should have a repeat test two to four months after return.
• Vaccination against hepatitis A is recommended for all travelers to developing countries. Some expert groups also believe that such travelers should have hepatitis B vaccinations as well, but the CDC does not generally recommend them at this time except under certain circumstances.
• Travelers to countries with malaria should take preventive agents.
• Some countries may require vaccinations against yellow fever, meningitis, typhoid, cholera, Japanese encephalitis, and rabies under certain circumstances. Some of these are covered in this report.
• Studies indicate that multiple vaccines may be given at the same time to most adults without significantly increasing adverse effects.

[Also for more information, see In-Depth Report #1: Travel to developing countries.]

Side Effects and Anti-Immunization Groups

Of great concern are anti-immunization organizations and websites, which were formed mostly because of unsubstantiated reports which linked small numbers of serious problems to some vaccines. The following watchdog systems are now in effect to monitor side effects from vaccination:

• VAERS (Vaccine Adverse Event Reporting System) is a government service that it registers all adverse events reported after vaccination, including those not related to the vaccine. It is useful for surveillance, but has limitations. For example, it may record the same case more than once. In addition, more serious events that occur after a vaccination are more likely to be reported than later and milder events, and such events are not necessarily linked to the vaccine.
• VSD (Vaccine Safety Datalink) is a linked database that analyses the records of over seven million patients. It is more accurate than VAERS, although its information is not as timely.
• The CDC has established the national network of Clinical Immunization Safety Assessment (CISA) Centers. It will provide services to physicians to help them evaluate and manage patients who may have had a side effect.

Studies using these systems are ongoing and none to date have confirmed reports of any significant association between most vaccines and severe side effects that would outweigh the benefits of these important and life-saving agents. For example, a 2001 analysis that examined VSD data confirmed the overall safety of the childhood MMR and DTP vaccines.

Granted, no vaccine is 100% safe. Allergic and serious reactions are possible. In two cases, the early polio vaccine and the rotavirus vaccine, problems did occur, some serious. It is important to note, however, that even in these cases, the vaccines were withdrawn and the severe events still were far fewer than the lives saved.

The focus on vaccination side effects is ironic due to the fact that reports of such adverse effects outnumber the number of actual infections. Because vaccinations have been in existence for so long, today's parents have no direct knowledge of the consequences of these dreaded infections, which killed or severely sickened millions of children in the past.

It should be noted that studies are reporting that the risk for infection increases significantly in children who are not vaccinated. There is also a rise in infections among immunized children, suggesting resistance to the vaccines.