Traveller vaccination hepatitis E

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]

Disease cause

Hepatitis E virus (HEV). It has four known genotypes that infect mammalian hosts (genotypes 1, 2, 3 and 4).

Transmission

The virus is usually acquired through contaminated drinking-water. Direct faecal–oral transmission from person to person is also possible. There is no insect vector. Various domestic animals, including pigs, may be reservoirs of HEV.

Nature of the disease

The clinical features and course of the disease are generally similar to those of hepatitis A (see above). However, during the third trimester of pregnancy HEV infection is more serious and is associated with case–fatality rates reaching 20% or higher. In addition to pregnant women, those with pre-existing liver disease and immunosuppressed persons are at greater risk for severe disease following HEV infection.

Geographical distribution

HEV is a leading cause of acute viral hepatitis in developing countries. Each year HEV genotypes 1 and 2 may account for about 20.1 million HEV infections, 3.4 million symptomatic cases, 70 000 deaths and 3 000 stillbirths.

Risk for travellers

Travellers to developing countries may be at risk when exposed to poor conditions of sanitation and drinking-water control.

Vaccine

• A vaccine against HEV has recently been developed and licensed in China. The vaccine contains a recombinant viral capsid protein corresponding to genotype 1 of HEV, but is likely to protect against all four genotypes. Three doses of the vaccine are given intramuscularly at 0, 1 and 6 months. So far, this vaccine has shown a favourable safety profile as well as excellent immunogenicity and clinical efficacy when used in healthy individuals aged 16-65 years.

• The duration of protection is at least two years. Because of a lack of sufficient information on safety, immunogenicity and efficacy in important target groups such as children under 16 years of age, pregnant women and people with chronic hepatic disorders, WHO does not currently recommend this vaccine for routine use in national programmes of endemic countries. However, vaccination against HEV may be considered in special situations where the risk of contracting HEV is particularly high. For example, WHO recognizes the high risk of HEV infection for travellers, health-care and humanitarian relief workers deployed or travelling to areas where there is an ongoing outbreak of hepatitis E. In such circumstances, each person should be evaluated individually for risks and benefits of vaccination against HEV.

Precautions

Travellers should follow the general recommendations for avoiding potentially contaminated food and drinking-water (Chapter 3).

Summary of vaccine data

	Considerations for travellers for Hepatitis E vaccination
Type of vaccine	Recombinant vaccine based on genotype 1 capsid protein which cross-protects against all 4 genotypes of hepatitis E virus of human relevance.
Number of doses	3 (administered intramuscularly at 0, 1 and 6 months). The possible need for booster doses after >2 years is not yet defined.
Contraindications	Not described, except for serious allergy to vaccine components.nsitivity to previous dose.
Adverse reactions	Rare local reactions.
Before departure	4 weeks.
Indication	Travellers, health-care and humanitarian relief workers travelling to areas during outbreaks of hepatitis E.
Special precautions	So far, no safety data are available on its use in children, the elderly, pregnant women, or patients with chronic liver disease or immunodeficiencies.