From the Guidelines
Hepatitis A antibody (HAV Ab) testing is crucial for determining immunity against hepatitis A, and vaccination is the most effective means of preventing HAV transmission, especially for high-risk individuals. The hepatitis A vaccine is prepared from formalin-inactivated, cell-culture–derived HAV and is available in two monovalent vaccines (Havrix and Vaqta) approved by the FDA for persons aged ≥12 months 1. The vaccine induces protective antibody levels among virtually all adults, with 94%–100% of adults having protective antibody levels by 1 month after the first dose, and 100% achieving protective levels after a second dose 1. Key points about hepatitis A antibody testing and vaccination include:
- Hepatitis A antibody testing detects antibodies produced in response to hepatitis A virus infection or vaccination
- A positive result indicates either previous infection or successful vaccination, meaning you have immunity against hepatitis A
- A negative result suggests no prior exposure to the virus and no immunity, indicating you may benefit from vaccination
- The test specifically looks for IgM antibodies (indicating recent infection) or total/IgG antibodies (indicating past infection or vaccination)
- Vaccination is recommended for high-risk individuals, such as MSM, injecting drug users, and persons with chronic liver disease, who did not receive hepatitis A vaccination during childhood 1. Vaccination with a 2-dose series at 0 and 6–12 months is the most effective way to prevent HAV transmission and induce long-term protective antibody levels. Kinetic models of antibody decrease among adults indicate that protective levels persist for >40 years 1. A study of Alaska Natives demonstrated that seropositivity for hepatitis A persists for >20 years after completing 2-dose vaccination at age 12–21 months 1. Healthcare providers typically order hepatitis A antibody testing when evaluating liver function abnormalities, investigating jaundice, screening high-risk individuals, or confirming immunity status before travel to regions where hepatitis A is common.
From the Research
Hepatitis A Antibody (HAAB)
- Hepatitis A virus (HAV) is one of the most common infectious etiologies of acute hepatitis worldwide, transmitted fecal-orally, and can also be transmitted through oral-anal sex 2.
- The duration of HAV viremia and stool shedding of HAV may be longer in human immunodeficiency virus (HIV)-positive individuals compared to HIV-negative individuals with acute hepatitis A 2.
- Current guidelines recommend HAV vaccination for individuals with increased risks of exposure to HAV or with increased risks of fulminant disease, such as those with chronic hepatitis 2.
Prevention and Prophylaxis
- Immune globulin has been used as an effective means of protecting individuals against HAV infection and disease, with approximately 90% efficacy in preventing hepatitis A 3.
- Hepatitis A vaccine has been shown to be effective in preventing HAV infection, with seroconversion rates following the recommended standard adult dosing schedule being lower among HIV-positive individuals compared to HIV-negative individuals 2.
- A study comparing hepatitis A vaccine with immune globulin for postexposure prophylaxis found that both provided good protection after exposure, although the vaccine may have slightly lower efficacy 4.
Recommendations for Use
- The American Academy of Pediatrics Committee on Infectious Diseases recommends the use of hepatitis A vaccine for pediatric patients, including travelers to areas with intermediate to high rates of endemic hepatitis A, children living in defined and circumscribed communities with high endemic rates or periodic outbreaks of HAV infection, and patients with chronic liver disease 5.
- Immune globulin is recommended for postexposure prophylaxis, as vaccine has not yet been demonstrated to be protective for this purpose 5.