- important new information regarding the effectiveness of hepatitis A vaccine for postexposure prophylaxis
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For most, the best hepatitis A postexposure prophylaxis is vaccination
Victor JC, Monto AS, Surdina TY, et al. Hepatitis A vaccine versus immune globulin for postexposure prophylaxis. N Engl J Med. 2007;357:1685–1694.
The objective of this investigation, conducted in Almaty, Kazakhstan, was to compare the relative effectiveness of hepatitis A vaccine with that of immune globulin for prophylaxis after exposure to the hepatitis A virus. Participants were 2 to 40 years old and were household or day-care contacts of people who had hepatitis A. Five hundred sixty-eight susceptible patients received hepatitis A vaccine within 14 days of exposure; 522 susceptible patients received an age-appropriate dose of immune globulin. The primary endpoint was laboratoryconfirmed, symptomatic hepatitis A within 15 to 56 days of exposure.
FIGURE 1 Hepatitis A virus
Hepatitis A virus has single-stranded RNA, no envelope, and is approximately 27–30 nm in diameter.Symptomatic infection occurred in 25 of 568 (4.4%) vaccine recipients and 17 of 522 (3.3%) recipients of immune globulin. The relative risk of infection after the vaccine was 1.35 (95% confidence interval [CI], 0.70–2.67). No serious adverse effects occurred as the result of administration of either the vaccine or immune globulin. The authors concluded that both agents provide effective postexposure prophylaxis against hepatitis A infection.
Hepatitis A is caused by an RNA virus that is transmitted by fecal–oral contact. It is highly contagious and endemic in areas of the world where poverty, poor sanitation, and overcrowded living conditions prevail. Hepatitis A usually causes a symptomatic illness characterized by fever, malaise, anorexia, jaundice, acholic stools, darkened urine, and hepatic pain and tenderness. In poorly nourished or immunocompromised patients, severe morbidity and, rarely, mortality, may occur. Unlike other forms of hepatitis, hepatitis A does not cause a chronic carrier state, and perinatal transmission is extremely unlikely.
Best strategy? Prevention
At present, there is no specific antiviral therapy that is routinely used for treatment of hepatitis A. However, highly effective preventive measures are available. For preexposure prophylaxis, time permitting, the ideal agent is inactivated hepatitis A vaccine.1
The vaccine is usually given in two doses separated by 6 to 12 months and is highly immunogenic. In the United States, key candidates for vaccination are
- gay men
- residents and staff of chronic care facilities
- intravenous drug users
- individuals who live in areas where hepatitis A is endemic
- primate laboratory workers
- people 30 years of age and older who have chronic liver disease
- international travelers
- people who have received a liver transplant or are awaiting one.
The vaccine is safe for administration in pregnancy and is now recommended for children.
After exposure, vaccine trumps immune globulin in healthy patients
The standard agent for prophylaxis after exposure to the hepatitis A virus has been immune globulin 0.02 mL/kg, administered intramuscularly. Immune globulin is highly effective in this application and, in the present investigation, it was slightly more effective than the vaccine.
Despite the modest difference in effectiveness, however, hepatitis A vaccine offers several unique advantages for postexposure prophylaxis:
- It confers long-term immunity rather than just temporary protection.
- Because the volume of fluid injected is lower, the vaccine causes less pain upon administration.
- Immune globulin is now produced by a single manufacturer, and its supply has been limited. Its price also approaches that of the vaccine.
- Administration of immune globulin to a child may disrupt the normal childhood immunization schedule.
In older and immunocompromised patients, use immune globulin
For most patients, hepatitis A vaccine is the indicated method of postexposure immunoprophylaxis.
Because it is slightly more effective, however, immune globulin probably should remain the preferred agent for hepatitis A postexposure prophylaxis in older or immunocompromised patients who are more likely to develop severe illness if they be-come infected.