OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

May 28, 1992

Susan E. Harwood, Ph.D. Director,
Office of Risk Assessment
U.S. Department of Labor
Occupational Safety and Health Administration
200 Constitution Avenue, N.W.,
Room N3718
Washington, D.C 20210

Dear Dr. Harwood:

Thank you for your recent inquiry regarding clarification of the recommendations when the hepatitis B vaccine schedule is interrupted.

The Immunization Practices Advisory Committee (ACIP) recommendations (MMWR 1991; 40:7) state that "If the vaccination series is interrupted after the first dose, the second dose should be administered as soon as possible. The second and third dose should be separated by an interval of at least 2 months. If only the third dose is delayed, it should be administered when convenient."

Studies have shown that the third dose of vaccine can be delayed for 1 year or longer after the first dose and the response is excellent. There are data that show that the interval between the first and second dose can be as long as 3 months without affecting seroconversion or antibody titers. Beyond that time, there are no data. However, as a result of discussion with ACIP members and other hepatitis experts, a conclusion was reached that in the event of interruption of the series after the first dose, the series did not have to be restarted. Instead, the second dose should be given as soon as possible, followed by the third dose at least two months after the second (as stated above). If the delay between the first and second dose is longer than 3 months and there is concern about the response to vaccine, then post-vaccination testing can be considered to determine that the vaccine recipient responded to the series.

I hope this helps clarify the recommendations. Please feel free to call me if you have further questions.


Craig N. Shapiro, M.D.
Medical Epidemiologist
Hepatitis Branch
Division of Viral and Rickettsial Diseases
National Center for Infectious Diseases