Elderly patients are at an increased risk of infection because of an age-related senescence of the immune system. Several mechanisms have been implicated in this decline of the immune response, including (1) impaired functioning of the thymus gland, (2) a decline in T-cell maturation and function, and (3) a reduced B-cell response.

Although these factors are associated with an attenuated immune response to offending organisms, the etiologic mechanism of these impairments is not fully understood. Proposed mechanisms include nutritional deficiencies, declining cyto-kine levels, and changes in intercellular messenger responses. The increased prevalence of chronic disease and medication use may well account for much of the decline in immune function observed in older people. The resulting immunosenescence can impair the host’s ability to mount a proper immune response to vaccines. Unfortunately, there is no proven reliable predictor of immune system viability.
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Cellular immunity refers to the immune response that is mediated primarily by lymphocytes and macrophages. This portion of the immune system is responsible for killing viruses and tumor-containing cells, mounting delayed hypersensitivity reactions, and rejecting transplanted organs. Dysfunction of the thymus gland has been implicated as one cause of the observed age-related decline in cellular immunity in the elderly. Investigators have discovered that the serum concentrations of thymic hormone decline with age.

Humoral-mediated immunity refers to the immune response that is mediated primarily by antibodies and complement proteins produced by mature B lymphocytes. The humoral response accounts for antigen-specific and nonspecific immunity-to-host invaders.

Antibody production is compromised in elderly patients. One postulated cause is altered B-cell and immunoregulatory T-lymphocyte function. In the elderly, these deficiencies can result in lower than expected antibody responses to vaccinations.

VACCINES

The following vaccines are recommended for use in elderly patients:

  • hepatitis B vaccine
  • influenza vaccine
  • measles-mumps-rubella (MMR) vaccine
  • 23-valent pneumococcal polysaccharide vaccine
  • tetanus-diphtheria toxoid
  • varicella vaccine

Because many of the elderly have active immunity to MMR and varicella from vaccination or childhood disease and because hepatitis B vaccine is recommended only for a small group of elderly patients, vaccination campaigns are targeted at pneumococcus, tetanus, and influenza. Despite these efforts, a large portion of older adults remain at risk for vaccine-preventable disease. Influenza and pneumococcal disease account for 50 to 100 times more deaths than all other vaccine-preventable diseases combined. Together, these illnesses represent the fifth leading cause of death among the elderly. canadian antibiotics

Failure to effectively inoculate elderly patients whose vaccinations are not up to date contributes greatly to this risk. The fact that many elderly people are afflicted with chronic diseases (e.g., diabetes and cardiovascular, pulmonary, and renal diseases) further complicates the efficacy of these programs. These disorders may decrease the immunogenicity of some vaccines, rendering them less effective.

Two major sources of information on vaccines for adults in the U.S. are the National Coalition for Adult Immunization (NCAI) and the Advisory Committee on Immunization Practices (ACIP). Established in 1988, the NCAI consists of 130 organizations, including professional associations, voluntary organizations, advocacy groups, vaccine manufacturers, government health agencies, and state and local coalitions. Its goal is to improve vaccine use in adults by educating health care providers and patients about vaccines. The NCAI maintains a Web site of vaccine-related materials for patients and health care providers.

The ACIP also issues vaccine recommendations in the U.S. This 15-member committee is selected by the Secretary of the U.S. Department of Health and Human Services (DHHS) to provide advice and guidance to the Secretary, the Assistant Secretary for Health, and the Centers for Disease Control and Prevention (CDC) on the most effective means to avoid vaccine-preventable diseases. During January of each year, the ACIP issues recommendations for the routine administration of vaccines to children and adults, including schedules, dosages, and contraindications applicable to each vaccine. These recommendations are published in the CDC’s journal, Morbidity and Mortality Weekly Reports, and in Annals of Internal Medicine.