Risk of Occupational Exposure to Hepatitis B Virus (HBV)
Hepatitis B virus (HBV) is very efficiently transmitted in the setting of a percutaneous injury that involves an instrument coated with or containing HBV-infected blood. The risk of acquiring HBV from a needlestick injury ranges from 1% to 6% (source patient HBsAg-positive, HBeAg-negative) to 22% to 40% (source patient HBsAg-positive, HBeAg-positive). The risk of hepatitis C virus (HCV) and HIV transmission with a comparable exposure is much lower: 3% to10% and 0.2% to 0.5%, respectively (Figure 1). Acquisition of HBV virus can also occur via contact of mucous membranes or non-intact skin with infectious blood or body fluid. The risk of non-percutaneous exposure has not been well quantified, but it may account for a significant proportion of HBV transmission in the healthcare setting. Indeed, many healthcare workers infected with HBV cannot recall an overt needlestick injury, but can remember caring for a patient with hepatitis B. Hepatitis B virus is a hardy virus that can survive in dried blood for up to a week and thus may be transmitted via discarded needles or fomites, even days after initial contamination. The highest concentrations are in blood and serous fluid. Although HBV DNA has been detected in other body fluids, including saliva, nasopharyngeal secretions, semen, or vaginal fluid, to the best of our knowledge, occupational transmission of HBV from these exposures has not yet been documented. Available data would suggest that transmission is unlikely to occur through contact with urine or feces.
Epidemiology of Hepatitis B in Healthcare Workers
Epidemiologic studies in the United States in the 1970's demonstrated that healthcare workers (HCWs) had a seroprevalence rate of HBV infection that was 5 to 10 times higher than the general population. Clinicians with direct patient contact, such as physicians, dentists, nurses, and dialysis workers, are at higher risk of acquiring HBV. Laboratory workers and cleaning staff also have higher than average rates of exposure to HBV. In 1983, the HBV vaccine became available in the United States, and in 1991, OSHA required health care facilities to offer free HBV vaccination to any employee at risk for exposure. Between 1983 and 1995, the incidence of HBV infection in United States HCWs decreased by a striking 95% percent, likely as a result of the increased use of HBV vaccine among health care workers in the latter part of this period. Unfortunately, a significant proportion of United States HCWs stlll do not receive HBV immunization, and remain susceptible to HBV infection. In one 2009 national survey conducted by the Centers for Disease Control and Prevention, up to 25% of health care workers reported never receiving a dose of hepatitis B vaccine and almost a third never completed the full vaccine series. Similar findings were noted in a hospital-based cross-sectional study, with 71% coverage rates observed even among workers such as phlebotomists who were particularly at risk for HBV exposure. The vaccine refusal rate was lowest in groups at higher risk of exposure to HBV, but even among nurses, nearly 30% chose to forego vaccination. In addition, 5 to 10% of employees who undergo the initial vaccination series may have an inadequate hepatitis B antibody response (defined as serum antibody titers less than 10 mIU/ml)[8,13]. Thus, systematic availability of HBV postexposure prophylaxis procedures remains critical in order to reduce the risk of occupational HBV infection in susceptible HCWs.
Hepatitis B Immunoglobulin (HBIG) for Postexposure Prophylaxis
Hepatitis B immune globulin (HBIG) is an important component of hepatitis B postexposure prophylaxis. An adequate dose of HBIG provides immediate neutralizing antibody directed against HBV. In most instances, HBIG is intended to serve as a short-term bridge in the control of HBV until the immune system can mount long-term protective response. Hepatitis B immune globulin is prepared from pooled human sera known to contain anti-hepatitis B antibodies. Donated sera are screened and processed to eliminate virtually any potential transfer of infectious HIV, HBV, or HCV. The recommended dose for HBIG is 0.06 ml/kg given by intramuscular injection. Hepatitis B immune globulin may be given concurrently with the hepatitis B vaccine, but should be given at a different anatomic site, such as the gluteal muscles or opposite deltoid muscle. Serum anti-HBs levels typically peak 1 week after injection, and the mean half-life of HBIG is 22 days. In the absence of concomitant administration of giving HBV vaccine, multiple doses of HBIG provide an estimated 75% protection from acquiring HBV in the occupational exposure setting. Adverse reactions to HBIG are unusual but can include pain at the injection site and allergic reactions (urticaria, angioedema, and rarely anaphylaxis). A history of anaphylaxis to any immune globulin (IG) preparation is a contraindication to receiving HBIG. The use of HBIG is considered safe for women who are pregnant or lactating.
Hepatitis B Vaccine and Postexposure Prophylaxis
HBV vaccine is used in the postexposure prophylaxis setting to augment the immune response to hepatitis B. Two HBV vaccines are approved for use in adults; both require administration of three separate injections into the deltoid muscle (Figure 2). In addition, if the HCW has an additional indication for receiving hepatitis A vaccine, they can receive the combination HAV and HBV vaccine. The efficacy of the combination of HBIG and HBV vaccine in reducing the rate of HBV infection acquired through occupational exposure has not been demonstrated directly, but its advantage is inferred because the combined regimen demonstrated an 85-95% efficacy in preventing perinatal transmission of HBV[3,14].
Evaluation and Management of Occupational Exposure to HBV
In 2001, the United States Public Health Service (USPHS) published guidelines for the evaluation and potential use of postexposure prophylaxis following occupational exposures to HBV, HCV and HIV. These guidelines emphasize that all healthcare facilities in the United States should have specific protocols for HCWs who have potential for exposure to patient bodily fluids. Immediately after the exposure occurs, the HCW should wash wound and skin sites thoroughly with soap and water, and flush exposed mucous membrane sites with water. Next, the employee should promptly undergo an evaluation that includes recording of details of the exposure (time, date, type, and site), known information on the source patient (HIV, HBV, and HCV status), and the employee's relevant health history (including hepatitis B immunization status and post-immunization titer). If the source patient can be identified, they should undergo testing for HBV, HCV, and HIV, unless these results are already known. Multiple factors should be taken into account to determine whether postexposure prophylaxis for HBV is warranted (Figure 3). If the exposure is deemed to confer a significant risk for HBV transmission, the USPHS guidelines recommend prompt initiation of postexposure prophylaxis. As outlined in detail below, the specific type of postexposure prophylaxis is based on the HCW's prior receipt of HBV vaccine and their immune response to the vaccine.
The utility of initiating postexposure prophylaxis more than 7 days from the exposure is unclear. If the exposure occurred more than 7 days prior, the hepatitis B vaccine should be given (if indicated), but use of HBIG should be considered on a case-by-case basis, ideally with expert consultation. Similarly, for instances in which the source patient is unidentifiable, such as a needlestick injury involving a needle in a sharps container or from bed linens, the decision whether to provide HBV postexposure prophylaxis should be made on a case-by-case basis, and may require expert consultation, particularly for decisions that involve giving HBIG.
HCW Not Previously Vaccinated
If a HCW has neither a history of receiving hepatitis B vaccine nor evidence of prior HBV infection, they should be presumed to be at significant risk of acquiring HBV infection following an exposure. In this situation, HBIG is indicated if the source of the exposure is HBsAg positive or if the hepatitis B status of the source is unknown or cannot be assessed, but they belong to a high-risk group (men who have sex with men, injection-drug use, prior residence in a HBV-endemic region). The HBIG (0.06 mL/kg IM) should be administered to the HCW within one week of the exposure, preferably within 24 hours (Figure 4). The HCW should also receive the first dose of the HBV vaccine series, ideally concurrently. In instances in which the source patient is unidentifiable, such as a needlestick injury involving a needle in a sharps container or from bed linens, the indication for HBV postexposure prophylaxis should be made on a case by case basis, preferably with expert consultation.
HCW Previously Vaccinated with Effective Response to Vaccine
If an exposed employee was vaccinated for HBV and had a documented post-vaccination anti-HBs antibody titer greater than 10 mIU/ml, they would not need postexposure prophylaxis for hepatitis B. In many individuals, serum levels of anti-HBs wane and decline slowly after vaccination to a level less than 10 mIU/ml after vaccination, but it is unclear whether a remotely vaccinated employee who responded to the vaccine needs a booster for hepatitis B after an exposure. It is reasonable to consider a booster vaccination if the healthcare worker was vaccinated more than 10 to 20 years prior to the exposure, particularly if the exposure was relatively high risk (hollow-bore needle and a HBeAg-positive source patient).
HCW Previously Vaccinated with Lack of Response to Vaccine
Individuals who did not respond to previous attempts at HBV immunization (post-vaccine titers less than 10 mIU/ml) pose a special challenge, since they may not derive benefit from HBV vaccine given in the postexposure setting. In this case, two options are acceptable: (1) administer a single dose of HBIG at the time of exposure and repeat the hepatitis B vaccine series, or (2) administer a dose of HBIG at the time of exposure and repeat a second dose of HBIG one month later. For those employees who have previously failed to respond to two vaccine series, most experts would recommend the latter approach, with the assumption that an additional HBV vaccine series would not generate a significant immune response.
HCW Previously Vaccinated with Unknown Response to Vaccine
If the exposed employee's post-vaccination titer is unknown, anti-HBs titers should be measured. Again, HCWs whose anti-HBs titers demonstrate levels greater than 10 mIU/ml do not need postexposure prophylaxis. Employees whose antibody titers are less than 10 mIU/ml are treated similarly to non-responders (Figure 4). If the turnaround time for titer results is more than 48 to 72 hours or if the employee has multiple risk factors for poor vaccine response (greater than 50 years of age, smoking, obesity, renal failure or immunosuppression), then postexposure prophylaxis with HBIG and the hepatitis B vaccine can be initiated pending lab results.
Use of Antivirals or Interferon for Postexposure Prophylaxis
Although antiviral medications have been successfully used for HIV postexposure prophylaxis, as well as to reduce HBV transmission after liver transplantation, data are insufficient to recommend the use of antiviral postexposure prophylaxis for HBV in the occupational setting. Similarly, although use of an interferon-based product would have theoretical benefit, no data exist to support its use in the setting of HBV exposure. The 2001 USPHS guidelines for management of occupational exposure to HBV do not recommend the use of antivirals or any interferon-based product for postexposure prophylaxis.
Follow-up and Monitoring of Health Care Worker
Post-vaccination titers should be obtained on all HCWs who received the HBV vaccine. For those who receive HBIG, it is important to wait 4 to 6 months after HBIG administration before anti-HBs titers are drawn in order to accurately assess the HCW's immune response to HBV vaccine (as opposed to detecting remnant antibodies from the administered HBIG). Although no guidelines exist regarding follow-up of HCWs after an HBV exposure, we would recommend follow-up serology testing (measurement of HBsAg and anti-HBc) at 3 and 6 months after the exposure.
1 Sepkowitz KA. Occupationally acquired infections in health care workers. Part II. Ann Intern Med. 1996;125:917-28.PubMed Abstract
2 Gerberding JL. Management of occupational exposures to blood-borne viruses. N Engl J Med. 1995;332:444-51. PebMed Abstract
3 Updated U.S. Public Health Service guidelines for the management of occupational exposures to HBV, HCV and HIV and recommendations for postexposure prophylaxis. MMWR Morb Mortal Wkly Rep 2001;50(RR-11):1-52. CDC and Prevention
4 Mahoney FJ, Stewart K, Hu H, Coleman P, Alter MJ. Progress toward the elimination of hepatitis B virus transmission among health care workers in the United States. Arch Intern Med 1997;157:2601-5.PubMed Abstract
5 Louther J, Feldman J, Rivera P, Villa N, DeHovitz J, Sepkowitz KA. Hepatitis B vaccination program at a New York City hospital: seroprevalence, seroconversion, and declination. Am J Infect Control. 1998;26:423-7.PubMed Abstract
6 Doebbeling BN, Ferguson KJ, Kohout FJ. Predictors of hepatitis B vaccine acceptance in health care workers. Med Care. 1996;34:58-72.PubMed Abstract
7 Agerton TB, Mahoney FJ, Polish LB, Shapiro CN. Impact of the bloodborne pathogens standard on vaccination of healthcare workers with hepatitis B vaccine. Infect Control Hosp Epidemiol. 1995;16:287-91.PubMed Abstract
8 Kubba AK, Taylor P, Graneek B, Strobel S. Non-responders to hepatitis B vaccination: a review. Commun Dis Public Health. 2003;6:106-12. PubMed Abstract
9 Floreani A, Baldo V, Cristofoletti M, Renzulli G, Valeri A, Zanetti C, Trivello R. Long-term persistence of anti-HBs after vaccination against HBV: an 18 year experience in health care workers. Vaccine. 2004;22:607-10.PubMed Abstract
10 Kidd-Ljunggren K, Holmberg A, Bläckberg J, Lindqvist B. High levels of Hepatitis B virus DNA in body fluid from chronic carriers. J Hosp Infect. 2006;64:352-7. PubMed Abstract
11 Lu PJ, Byrd KK, Murphy TV, Weinbaum C. Hepatitis B vaccination coverage among high-risk adults 18-49 years, 2009. Vaccine. 2011;29:7049-57. PubMed Abstract
12 Simard EP, Miller JT, George PA, Wasley A, Alter MJ, Bell BP, Finelli L.Hepatitis B vaccination coverage levels among healthcare workers in the United States, 2002-2003. Infect Control Hosp Epidemiol. 2007;7:783-90PubMed Abstract
13 Sjogren MH. Prevention of hepatitis B in nonresponders to initial hepatitis B virus vaccination. Am J Med. 2005;118 Supplement 10A;34S-39S. PubMed Abstract
14 Mast EE, Weinbaum CM, Fiore AE, et. al. A comprehensive immunization strategy to eliminate transmission of hepatitis B infection in the United States: recommendations of the Advisory Committee on Immunization Practices Part II: Immunization of adults. MMWR Recomm Rep. 2006;55:1-33.CDC