HBV vaccinations and age

April 1, 2003
The hepatitis B virus (HBV) is a major cause of viral hepatitis, cirrhosis, liver failure, and liver cancer worldwide. Infection readily occurs when infected blood and other body fluids enter the body of a susceptible person.

Charles John Palenik, MS, PhD

The hepatitis B virus (HBV) is a major cause of viral hepatitis, cirrhosis, liver failure, and liver cancer worldwide. Infection readily occurs when infected blood and other body fluids enter the body of a susceptible person. Traditionally, dental personnel have been at increased risk for HBV infection. Their frequent exposure to blood and saliva dramatically increase the chances of occupational acquisition.

More than 90 percent of children infected at birth develop chronic illness. The numbers drop to 30 percent for those infected between the ages of one and five years. Only 6 percent of those persons infected past the age of five become chronic carriers. Unfortunately, between 15 and 25 percent of chronically infected people eventually die from some form of liver disease. Serious symptoms can develop more than 20 years after acute infection. An estimated 1.25 million chronically infected people live in the United States; of this number, 20 to 30 percent acquired the infection during childhood.

The HBV vaccine is the best protection against infection. Two effective, safe vaccines have been available for more than 13 years. During the period from 1982 through 2002, an estimated 40 million infants and children and 30 million adults received the HBV-vaccine series. Twenty years ago, more than 250,000 new HBV infections occurred annually. That number declined to less than 78,000 in 2001.

The overwhelming majority of dental personnel has either been immunized or has suffered natural infections. Recognizing the occupational risk present among health care workers, the Occupational Safety and Health Administration in 1991 mandated employer-sponsored HBV vaccination for at-risk workers as part of its Bloodborne Pathogens Standard.

Recently, a meta-analysis of 24 publications studied the association of age with response to HBV vaccination. (Meta-analysis is a set of statistical procedures that accumulate experimental and correlational results across independent studies that address a related set of research questions.) This study found evidence of a strong association between older age and a nonprotective response to HBV vaccination. The risk was present for individuals young as age 30. The findings are biologically plausible considering the changes in cellular and humoral immune responses known to occur among older individuals. There was no evidence that either of the two commonly used vaccines was more immunogenic in older people. The routine use of a fourth injection or booster shots did not decrease the risk for nonresponders among older individuals.

These results are important and could affect dental practice HBV vaccination policies. A lack of response may include people young enough to be at-risk for long-term complications of chronic HBV infection.

The HBV vaccines used today are at least 90 percent effective when given properly to healthy, younger adults. Ideally, serologic screening should occur within a few months after the completion of the vaccine series. Levels of antibodies against HBV normally decline over time; however, immune memory remains intact indefinitely. Thus, serological screening years after immunization may indicate less than desired antibody levels, leading to the possibility of inadequate initial response. In such cases, a gastroenterologist should be consulted.

The leading source of safety and health information for dental practices, the Organization for Safety and Asepsis Procedures (OSAP) offers a wealth of compliance information. Visit the OSAP Web site — www.osap.org — for links to more topics.

Dr. Charles John Palenik is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik has authored numerous articles, book chapters and monographs, and is the co-author of the popular Infection Control and Management of Hazardous Materials for the Dental Team. He serves on the Executive Board of OSAP, dentistry's resource for infection control and safety.Questions about this article or any infection control issue may be directed to [email protected].

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