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| PNEUMOCOCCAL DISEASE |
Disease
The term “pneumococcal disease” refers to a group of clinical conditions caused by the bacterium Streptococcus pneumoniae. Invasive pneumococcal infections include pneumonia, meningitis and febrile bacteraemia; the common non-invasive conditions include otitis media, sinusitis and bronchitis. Infection is acquired by direct person-to-person contact via respiratory droplets or oral contact. There are many healthy, asymptomatic carriers of the bacteria, but there is no animal reservoir or insect vector. Several chronic conditions predispose to serious pneumococcal disease. Increasing pneumococcal resistance to antibiotics underlines the importance of vaccination.
Occurrence
Pneumococcal diseases are a worldwide public health problem. S. pneumoniae is the leading cause of severe pneumonia in children under 5 years of age, causing more than 700 000 deaths each year, mainly in developing countries. In industrialized countries, most pneumococcal disease occurs in the elderly.
Risk for travellers
While travel itself does not increase the risk of acquiring pneumococcal infection, access to optimal health care may be limited during travel increasing the risk of poor outcomes should disease occur. Certain conditions predispose to complications of pneumococcal infections, including sickle-cell disease, other haemoglobinopathies, chronic renal failure, chronic liver disease, immunosuppression after organ transplantation and other etiological factors, asplenia and dysfunctional spleen, leaks of cerebrospinal fluid, diabetes mellitus and HIV infection. Elderly individuals, especially those aged over 65 years, are also at increased risk for pneumococcal disease. Pneumococcal vaccine is recommended for travellers who belong to these high-risk groups.
Vaccine
Pneumococcal vaccines are directed against Streptococcus pneumoniae (pneumococcus); the vaccines contain polysaccharide from capsular pneumococci. Pneumococcal polysaccharide vaccine contains purified polysaccharide from 23 capsular types of pneumococci (PPV-23) whereas pneumococcal polysaccharide conjugate vaccine (adsorbed) contains polysaccharide from 7 capsular types (PCV-7), the polysaccharide being conjugated to protein. The conjugate vaccine is effective in young children.
Pneumococcal vaccination is recommended for individuals at increased risk of pneumococcal infection as follows;
- age over 65 years
- asplenia or splenic dysfunction (including homozygous sickle cell disease and coeliac disease which could lead to splenic dysfunction);
- chronic respiratory disease (includes asthma treated with continuous or frequent use of a systemic corticosteroid);
- chronic heart disease;
- chronic renal disease;
- chronic liver disease;
- diabetes mellitus requiring insulin or oral hypoglycaemic drugs;
- immune deficiency because of disease (e.g. HIV infection) or treatment (including prolonged systemic corticosteroid treatment);
- presence of cochlear implant;
- conditions where leakage of cerebrospinal fluid may occur;
- Child under 5 years with a history of invasive pneumococcal disease.
Where possible, the vaccine should be given at least 2 weeks before splenectomy, cochlear implant surgery, and chemotherapy; patients should be given advice about increased risk of pneumococcal infection. Prophylactic anti-bacterial therapy against pneumococcal infection should not be stopped after immunisation.
Choice of vaccine- The 7-valent pneumococcal polysaccharide conjugate vaccine (PCV-7) is now a component of the primary course of childhood immunisation. The recommended schedule consists of 3 doses, the first at 2 months of age, the second at 4 months, and the third at 13 months.
Children at increased risk of pneumococcal infection should receive pneumococcal polysaccharide conjugate vaccine (PCV-7) at the recommended ages, followed by a single dose of the 23-valent pneumococcal polysaccharide vaccine (PPV-23) after their second birthday. Children at increased risk of pneumococcal infection presenting late for vaccination should receive 2 doses (separated by at least 1 month) of pneumococcal polysaccharide conjugate vaccine (PCV-7) before the age of 12 months and a third dose at 13 months. Children over 12 months and under 5 years (who have not been vaccinated or not completed the primary course) should receive a single dose of. pneumococcal polysaccharide conjugate vaccine (PPV-23) while 2 doses separated by an interval of 2 months in the immunocompromised or those with asplenia or splenic dysfunction). All children under 5 years at increased risk of pneumococcal infection should receive a single dose of the 23-valent pneumococcal polysaccharide vaccine (PPV-23) after their second birthday (and at least 2 months after the final dose of the 7-valent pneumococcal polysaccharide conjugate vaccine (PCV-7)).
Children over 5 years and adults who are at increased risk of pneumococcal disease should receive a single dose of the 23-valent unconjugated pneumococcal polysaccharide vaccine. (PPV-23) In some countries, such as the USA, routine vaccination is recommended for everyone aged over 65 years.
Revaccination In individuals with higher concentrations of antibodies to pneumococcal polysaccharides, revaccination with the 23-valent pneumococcal polysaccharide vaccine (PPV-23) more commonly produces adverse reactions. Revaccination is therefore not recommended, except every 5 years in individuals in whom the antibody concentration is likely to decline rapidly (e.g. asplenia, splenic dysfunction and nephrotic syndrome). Normally not more than two doses are given unless or until especially indicated.
It is advisable that children be uptodated with immunization, as per the national recommendations, before undertaking travel. |
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