Curbing Hepatitis A

Hepatitis A (HAV) is caused by an RNA virus of the Picornaviridae family, which includes the enteroviruses and rhinoviruses. Humans are the only reservoirs of HAV, which is spread by person-to-person contact, mainly by the faecal-oral route. The virus is discharged from the body of an infected person, who may or may not have symptoms.

The HAV is a hardy virus that can survive for months under favourable environmental conditions. Close personal contact with an infected person and the ingestion of contaminated water and food are the most common modes of spread. Blood-borne transmission of HAV is uncommon.

HAV does not damage cells by itself but the HAV infection leads to an immune response that damages liver cells. Clinical features of HAV infection are no different from that of other acute viral liver infections.

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Symptoms and Complications

Typical symptoms include fever, poor appetite (anorexia), nausea, tiredness and abdominal discomfort, which are followed by jaundice and the passage of dark-coloured urine. An infected person is most infectious about two to three weeks before, and a week after, the onset of symptoms.

The complications of HAV infection include relapsing and fulminant hepatitis. The latter occurs in about 0.01% of HAV infections. There is rapid deterioration of liver function in such a situation, leading to liver failure with a high likelihood of death.

The likelihood of symptoms is related to a person’s age. HAV infections in children below six years old are usually asymptomatic with about 10% developing jaundice. HAV infection in older children and adults are symptomatic in more than 70% of cases. There is no specific treatment available for HAV infections. Those who recover from HAV have life-long immunity.

HAV is a common infectious disease worldwide. The World Health Organisation (WHO) estimates that about 1.5 million people are infected annually. The incidence of HAV infections is related to socio-economic development. Many older third world countries have had HAV infections in their childhood when sanitation and food handling habits were less than desirable. Although HAV infection is usually self-limiting and rarely fatal, the suffering of those infected can be considerable.

HAV Vaccine

There are 4 types of HAV vaccine. They are given to adolescents and adults. There is no vaccine that is licensed for vaccinating infants.

A combined vaccine that contains HAV and recombinant hepatitis B vaccine is available for use in children above one year old. Although a single dose of the vaccine provides short-term protection, the manufacturers recommend a booster six to 12 months later to ensure long-term protection. The HAV vaccine may be given together with other vaccines in the national immunisation schedule or vaccines commonly given for travel.

It is advisable to defer immunisation when there is fever or an acute illness. Caution is necessary when the vaccine is used in those who have liver disease or allergies to neomycin (which is a component of the vaccine) and those who developed a hypersensitivity reaction in a previous injection. As the use of the vaccine in pregnancy and during breastfeeding has not been evaluated, it is not recommended for pregnant and lactating women.

Effectiveness and Safety

The HAV vaccines are very effective. More than 90% of vaccinees will develop sufficiently high levels of protective antibodies within a month of a single dose. Some studies report that 99 to 100% of vaccinees, who were given two doses of the vaccine, had high levels of antibodies five to eight years after immunisation. Study models indicate that the duration of protection is likely to be at least 20 years. The immunity after two doses of the vaccine is possibly life-long.

HAV vaccination is safe as complications are very rare. There have been millions of people given HAV vaccines without reports that statistically link adverse events to the vaccine. HAV vaccines are well tolerated. There may be pain, redness or swelling at the injection site. The more common systemic side effects are fever, tiredness, muscle or joint pains, abdominal discomfort, diarrhoea, nausea, vomiting and decreased appetite. Skin rashes or a nodule may appear at the injection site.

All adverse events are at most moderate and occur in the initial few days after vaccination. Recovery from the adverse events is usually spontaneous.

The HAV vaccine is safe and does not interfere with other vaccines given simultaneously. Its introduction has significantly reduced the incidence of HAV infection in many countries. Whether or not HAV vaccine is to be included in the national immunisation schedule is a matter for policy makers to decide. The decision will be influenced considerably by the cost-benefit of HAV immunisation.

More info on HEPATITIS A HERE.

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