HBV rates take plunge due to vaccinations
Researchers also probe need for booster doses
The number of hepatitis B infections among health care workers declined from 17,000 in 1983 to 400 in 1995 due to increased vaccination coverage, according to a recent study, but a substantial number of HCWs still have not received the full three-dose vaccine regimen.1
Study authors, mostly from the U.S. Centers for Disease Control and Prevention, point out that before licensure of recombinant-DNA-derived hepatitis B vaccine in 1986, approximately 12,000 HCWs were infected each year, with 250 HCW deaths per year from HBV-related chronic liver disease. Despite federal recommendations issued in 1982 that workers exposed to blood and body fluids receive pre-exposure prophylaxis with an earlier plasma-derived HBV vaccine,2 incidence of infection among HCWs remained high. Barriers to vaccinating HCWs included vaccine costs, concerns regarding the safety and efficacy of plasma-derived vaccines, and lack of perceived risk of HBV infection.
Emergence of the HIV epidemic in the mid-1980s brought increased recognition of risks associated with occupational exposure to infectious body fluids, eventually leading to publication of the federal bloodborne pathogens standard in 1991.3 The rule's requirement that employers provide hepatitis B vaccine at no charge to employees exposed to infectious body fluids resulted in "a substantial increase" in the numbers of HCWs offered and accepting vaccination, the study states.
"Much of this increase was a consequence of employee health program managers designating staff without direct patient contact as being eligible to receive hepatitis B vaccine and increased acceptance of hepatitis B vaccination by employees who previously had concerns about adverse effects from and the efficacy of the vaccine," the investigators say. The newer recombinant vaccines reduced concerns about vaccination safety.
Investigators found a steady decline in the number of HBV infections among HCWs from 1983, when the number was three times higher (386 per 100,000) than in the general U.S. population (122 per 100,000). By 1995, infections among HCWs decreased by more than 95% (9.1 per 100,000) and were more than fivefold lower than those in the general U.S. population (50 per 100,000), which had decreased by 60%.
To determine trends in disease incidence, researchers conducted telephone and fax surveys among a random sample of hospitals. A stratified sample was used based on number of hospital beds. The sample included 22 hospitals (11%) with 0-100 beds, 96 (48%) with 101-400 beds, and 82 (41%) with more than 400 beds. Interviews were conducted and a questionnaire administered to employee health program managers. Of the 200 hospitals contacted, 138 (69%) provided information of HBV vaccination programs, and 113 (56.5%) conducted employee health record reviews of 25 randomly selected employees to obtain vaccination information.
Of 2,837 hospital employees whose records were reviewed, employee health managers classified 2,532 (90%) as eligible to receive HBV vaccine. Of those employees, 66.5% had received all three doses. "That figure should be closer to 100%," says Miriam J. Alter, PhD, MPH, chief of the epidemiology section of the CDC's hepatitis branch and a co-author of the study.
"We've been recommending that health care workers at risk be vaccinated since 1982, and it's now 1998. Prior to OSHA requiring employers to offer vaccine to employees or have them sign a declination that they have refused, vaccination coverage was only around 40%. It substantially increased after the OSHA regulations went into effect. The OSHA regulations have been a significant factor in improving coverage," Alter says.
Other information that emerged from employee health vaccination records included:
· Vaccination coverage was highest for HCWs with frequent exposure to infectious body fluids (phlebotomists, laboratory personnel, and nursing staff).
· Vaccination coverage was lowest for employees at low risk for exposure (dietary and clerical staff).
· Vaccination coverage was highest for hospitals with 100 beds or fewer (86%), compared with hospitals with 101-400 beds (72%) and those with more than 400 beds (65%).
· Vaccination coverage was highest for Asian employees (82%), compared with coverage for Hispanic (76%), white (72%), and black (65%).
· No significant difference in vaccination coverage was found by type of hospital service, funding source, or metropolitan statistical area size.
Investigators found increased vaccination coverage in hospitals with certain policies:
· providing incentive encouragement;
· using employee performance measures, such as notifying a supervisor if an employee refused vaccination or imposing sanctions for refusing;
· requiring vaccination prior to employment;
· sending out reminder notices when vaccine doses were due;
· using a computerized tracking system.
Practices not associated with increased vaccination rates included vaccination campaigns, after-hours clinics, and vaccinating in individual work units.
The researchers suggest that improved compliance might be achieved through policies that directly affect employment or employee evaluations. In addition, they acknowledge that employee health managers might encounter more difficulties trying to vaccinate workers in large hospital settings.
Booster doses not needed for responders
An investigation into long-term protection after hepatitis B vaccination through a search of the medical literature revealed a decline in antibody titers to hepatitis B surface antigen (HBsAg) over time. However, the studies showed that vaccine-induced protection persists at least 11 years, even when antibody titers decline below detectable levels. The researchers conclude that vaccine booster doses are not needed for HCWs who have responded to vaccination and have a normal immune status.
Hepatitis B vaccination protection is directly related to the development of antibody against HBsAg. Adults who develop antibody titers to HBsAg of more than 10 mIU/ml after the vaccination series are virtually 100% protected from clinical illness and chronic infection. No studies or CDC case reports have demonstrated clinically significant, acute, or chronic HBV infections among adult vaccine responders. An anamnestic immune response after HBV exposure is the proposed mechanism for continued protection against HBV infection despite declining antibody titers, the researchers note.
"The vaccine only became available in mid-1982, so we only have follow-up until now. We will continue to evaluate the need for booster doses," Alter says.
References
1. Mahoney FJ, Stewart K, Hu H, et al. Progress toward the elimination of hepatitis B virus transmission among health care workers in the United States. Arch Intern Med 1997; 157:2,601-2,605.
2. Centers for Disease Control. Inactivated hepatitis B virus vaccine. MMWR 1982; 31:34.
3. U.S. Department of Labor, Occupational Safety and Health Administration. Occupational exposure to blood-borne pathogens: Final rule. 56 Fed Reg 64,004-64,182 (Dec. 6, 1991).
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