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| Hepatitis A |
Disease and occurrence
Although hepatitis A is rarely fatal in children and young adults, most infected adults and some older children become ill and are unable to work for several weeks or months. The case-fatality rate exceeds 2% among those over 40 years of age and may be 4% for those aged 60 years or more.
Risk for travellers
The vaccine should be considered for all travellers to areas with moderate to high risk of infection, and those at high risk of acquiring the disease should be strongly encouraged to be vaccinated regardless of where they travel. People born and raised in developing countries, and those born before 1945 in industrialized countries, have often been infected in childhood and are likely to be immune. For such individuals, it may be cost-effective to test for antibodies to hepatitis A virus (anti-HAV) so that unnecessary vaccination can be avoided.
Vaccine
Hepatitis A vaccines prepared from formaldehyde-inactivated hepatitis A virus grown in human diploid cells, are safe and effective.
Immunisation is recommended for:
- laboratory staff who work directly with the virus;
- staff and residents of homes for those with severe learning difficulties;
- workers at risk of exposure to untreated sewage;
- individuals who work with primates;
- patients with haemophilia treated with plasma-derived clotting factors;
- patients with severe liver disease;
- travellers to high-risk areas (see p. 673);
- individuals who are at risk due to their sexual behaviour;
- parenteral drug abusers.
Immunization should be considered for:
- patients with chronic liver disease as chronic hepatitis B or chronic Hepatitis C;
- Prevention of secondary cases in close contacts of confirmed cases of hepatitis A, within 7 days of onset of disease in the primary case.
- Hepatitis A, vaccine is administered to persons who are at least one year old. Anti-HAV antibodies are detectable by 2 week after administration of 1st dose of vaccine and good protection starts after 4 weeks after a primary inoculation.
A booster dose is usually given 6-12 months after the initial dose. A second booster dose can be given 25 years after the previous booster dose to those who continue to be at risk. Specialist advice should be sought on re-immunisztion of immunocompromised individuals.
For travellers given the long incubation period of hepatitis A (average 2–4 weeks), the vaccine can be administered to unimmunized individuals up to the day of departure and still protect travellers.
Passive immunization with immunoglobulin containing anti HAV antibodies has also been advocated before exposure or during the early incubation period after Hepatitis A virus infection. For post exposure prophylaxis of intimate contacts (household, sexual contacts and laboratory staff ), administration of 0.02 ml/kg of immunoglobulin is recommended as early after exposure as possible, it may be effective even when administered as late as 2 weeks after exposure. The use of immune globulin is now virtually obsolete for the purpose of herd prophylaxis.
A combination hepatitis A/typhoid vaccine is available for those exposed to waterborne diseases. The vaccine is administered as a single dose in unimmunized individuals and confers high levels of protection against both diseases. A second dose of hepatitis A vaccine is needed 6–24 months later and boosters of typhoid vaccine should be given at 3-yearly intervals.
A combination vaccine that provides protection against both hepatitis A and hepatitis B may be considered for travellers who may be exposed to both organisms. Primary immunization with the combined hepatitis A and B vaccine consists of three doses, given on a schedule of 0, 1 and 6 months. According to the manufacturer’s instructions, this combination vaccine may also be administered on days 0, 7 and 21, with a booster dose at 12 months. |
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