Hepatitis A and Hepatitis B (Twinrix)

Hepatitis A

Transmission
HA is transmitted via the fecal-oral route, which can occur from direct person-to-person contact, from contamination of the environment or objects, or through contaminated food or water. Transmission through infected blood or blood products has also been reported. Symptoms appear after an incubation period of 15 to 50 days (average 28 days). Cases are typically infectious two weeks before the onset of symptoms and remain infectious until a week after the onset of jaundice. The virus may remain infectious in the environment for several weeks. Viral shedding can be greatly prolonged in immunocompromised individuals.

Risk Factors
Persons at increased risk of HA infection include:

Travellers to HA endemic countries. Studies estimate that 44% to 55% of reported HA cases are linked to travel. Low-budget travellers, volunteer humanitarian workers, and Canadian-born children of new Canadians returning to their country of origin to visit friends and relatives, may be at increased risk.
Household or close contacts of an acute HA case.
Residents of certain institutions, such as correctional facilities and those for developmentally challenged individuals.
Men who have sex with men (MSM).
Illicit drug users. Increased risk is associated with low hygiene standards, contaminated drugs, and sharing of materials for oral or nasal use of drugs.
Household or close contacts of children adopted from HA endemic countries.
Residents in some Aboriginal communities. Higher risk may be attributed to inadequate water supplies and high housing density.
Hemophiliacs who use plasma-derived blood products.

DIN: 021877078 or 02231056

Hepatitis B

Transmission
HB is transmitted through percutaneous or mucosal contact with infectious biological fluids. Transmission of HB occurs through close contact with infectious bodily fluids, including through sharing of injection drug equipment (such as needles), sexual contact, and from mothers who are acute cases or carriers to their newborns. The risk of transfusion-related HB is extremely low because all blood and blood products are tested. Saliva is considered infectious in bite wounds with broken skin involving the inoculation of saliva, or when it is visibly tainted with blood. Almost one-third of people with HB infection have no identified risk factors.

Risk factors
The highest risk of transmission and of subsequent chronic carriage is in infants exposed during child birth to their mothers who are carriers of HB. Other groups at higher risk of HB include injection drug users, households with HB carriers and people at risk of sexually transmitted diseases. In Canada, most cases of acute HB occur in unimmunized people 25 years of age and older who acquire infection through unprotected sexual activity, sharing injection drug equipment, household contact with an HB carrier, or treatments or procedures with percutaneous exposure. People on dialysis are considered at high risk. A high proportion of HB carriers in Canada are immigrants from HB endemic areas.

DIN: 02230578 (Adult vaccine)

DIN: 02237548 (Junior vaccine)

Source : Public Health Agency of Canada