Pneumococcal VaccineStreptococcus Pneumoniae is an important cause of illness, hospitalization, and death world wide. In industrialized countries, invasive disease due to S. Pneumoniae is a serious problem among the elderly and those with chronic underlying medical conditions or immune systems that are compromised, either due to disease or immunosuppressive therapy.1 In Canada, 16% of community-acquired pneumonia among adults has been attributed to pneumococcus. Data from the Canadian Sentinel Health Unit Surveillance System in 1996 show incidence rates of culture positive invasive infection of 15/100,000 for all persons and 46/100,000 for persons >65 years of age. Mortality due to Pneumococcal pneumonia was 12.7% but was 20.3% among those >65 years of age.1 Recent Canadian laboratory based surveillance data indicate that 7% - 10% of the strains isolated from patients with invasive infection have reduced sensitivity to penicillin. Each year in the United States, pneumococcal diseases account for approximately 50,000 cases of bacteremia, 3,000 cases of meningitis, 100,000 to 175,000 hospitalizations from pneumonia, and 7 million cases of otitis media.4 Some pneumococci are encapsulated, their surfaces composed of complex polysaccharides. Encapsulated organisms are pathogenic for humans, whereas organisms without capsular polysaccharides are not. Capsular polysaccharides are the primary basis for the pathogenicity of the organism. They are antigenic and form the basis for classifying pneumococci by serotypes. Ninety serotypes have been identified, based on their reaction to type-specific antisera. Type-specific antibody to capsular polysaccharide is protective. Most S. pneumoniae serotypes have been shown to cause serious disease, but only a few serotypes produce the majority of pneumococcal infections. The 10 most common serotypes are estimated to account for about 62% of invasive disease worldwide. The current pneumococcal polysaccharide vaccine contains capsular polysaccharide of 23 types of pneumococci. Approximately 90% of cases of pneumococcal bacteremia and meningitis are caused by these 23 types. The six serotypes that most often cause drug resistant invasive pneumococcal infection are included in the vaccine. Efforts to develop effective pneumococcal vaccines began as early as 1911. However, with the advent of penicillin in the 1940s, interest in the vaccine declined, until it was observed that many patients still died despite antibiotic treatment. By the late 1960s, efforts were again made to develop a polyvalent pneumococcal vaccine. The current 23 valent polysaccharide vaccine was licensed in Canada in 1983. Efficacy, as measured by serotype-specific protection against invasive bacteremic pneumococcal disease, can surpass 80% among healthy young adults, but is in the range of 50% to 80% among the elderly and specific patient groups, such as persons with diabetes mellitis, anatomic asplenia, congestive heart failure or chronic pulmonary disease (evidence from case - control and retrospective cohort studies).5 Antibody response and clinical protection are decreased in certain groups at particularly high risk for pneumococcal infection. These include those with renal failure, sickle-cell anemia or impaired immune responsiveness. Although the vaccine may not be as effective in some persons, especially those who do not have normal resistance to infection, it is still recommended for such persons because they are at high risk of developing severe disease. NACI recommends immunization for groups at high risk of pneumococcal disease; however, vaccine programs and policies for who receives publicly funded vaccine are the responsibility of each province and territory. Revaccination: Results from serologic and case-control studies indicate that vaccine-induced immunity decrease with time. Because of the lack of evidence of improved protection with multiple doses of pneumococcal vaccine, routine revaccination of immunocompetent persons previously immunized with 23 valent-pneumococcal vaccine is not recommended.4 Persons for whom revaccination should be considered include those with functional or anatomic asplenia or sickle-cell disease; debilitating cardiorespiratory disease;hepatic cirrhosis; chronic renal failure; and immunosuppression related to disease or therapy. A single revaccination is recommended after five years in those aged >10 years of age. Any need for subsequent doses remains to be determined.5 A newly licensed heptavalent pneumococcal conjugate vaccine (PCV7), demonstrated to be safe and effective in preventing invasive pneumococcal disease when given to children presents new options for the control of IPD . However, this vaccine (Prevnar) is only recommended for children. PCV7 is currently not for use in adult populations and should not be used as a substitute for the PPV23 in the adult population.6 Studies among healthy adults >50 years of age, using Prevnar and among HIV-infected adults 18 to 65 years of age did not demonstrate substantially greater ELISA antibody concentrations after administration compared with PPV23. Also, the proportion of invasive pneumococcal isolates covered by PCV7 is only 50% to 60% among older children and adults, in contrast with 80% to 90% coverage by PPV23 among this older group.6 Adverse reaction reporting: All providers who administer vaccines should remember to report suspected adverse reactions to local public health authorities.2 The importance of this is shown by the experience of the 2000-2001 influenza vaccine program where an increased number of reactions characterized by bilateral red eyes (with or without discharge, itchiness, or edema) and at least one respiratory symptom (cough, sore throat, difficulty breathing, or wheezing) after administration of influenza vaccine were reported. After an extensive review this resulted in a change in the influenza vaccine manufacturing process for the 2001-2002 season, an increase in pre-season vaccine safety testing and modifications on guidelines for vaccine administration.2 Recommendations: Individuals >65 years of age should receive a dose of Pneumococcal vaccine on a onetime basis. Adults <65 years with high risk medical conditions for Pneumococcal infection should receive a single dose of Pneumococcal vaccine. Thanks to Dr. Graham L. Pollett MD, MHSc, FRCPC Medical Officer Of Health Middlesex London Health Unit, London Ontario for reviewing the draft copy of this article. References:
You can search for abstracts of the above references by following this link: PubMed Return to Archives Page ] [ Berries Home Page |