Reduced Doses of Hepatitis B Vaccines: Is It a Good Idea?

Article excerpt

When asked how long a person's legs should be, Abraham Lincoln replied "Long enough to reach the ground". A similar answer is perhaps required to the question of how much antigen should be put into a dose of hepatitis B vaccine: enough to do the job. Clearly, the well-executed study carried out by Goh et al. and reported in the previous article demonstrates that 10 [mu]g of of plasma-derived Merck, Sharpe & Dohme hepatitis B vaccine (now no longer produced) is enough to do the job in healthy young people in Singapore[1]. However, just as legs come in many varieties, so do hepatitis B vaccines, and we cannot assume that it is effective to use all hepatitis B vaccines in reduced doses to save costs.

Hepatitis B vaccines are not generic products: the optimal dose for each manufacturer's product is usually different and is deterrnined using dose titration curves in studies that vary the dose, age, schedule and sometimes the number of dose. For example, doses of 1.5 [mu]g, 2.5 [mu]g, 3 [mu]g, 5 [mu]g and 10 [mu]g of different vaccines are approved infant doses of hepatitis B vaccines in different countries. Some manufacturers try to build a "margin of safety" into their dose because the vaccine will be used under various conditions of storage and delivery and on humans of different sizes, ages, and immunocompetence. Other manufacturers market doses that may not allow for a reduction in dose. The performance of any vaccine "in the field" is usually less than that in carefully performed studies where the vaccine is properly stored and delivered on schedule, and where the recipients are often healthy young adults or children screened for factors that may reduce the immunogenicity of the vaccine.

Most hepatitis B vaccines are highly immunogenic (>90% seroconversion in controlled trials) in individuals aged up to 40 years; however, in older subjects reduced seroconversion may be encountered, which is related to age, male sex, obesity, and smoking. …


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