Safe and effective vaccines can prevent hepatitis A and B infections. A combined vaccine became available in many countries in 1997 in an adult formulation for patients 16 years and older following a zero-, one- and six-month administration schedule and in a pediatric formulation available for ages one to 16, following the same three-dose schedule. Combined vaccines can reduce the inconvenience and expense of administration.
With recent recommendations for a two-dose schedule of hepatitis B vaccination, van der Wielen and associates assessed the safety and immunogenicity of a two-dose vaccination schedule (zero and six months) using the adult formulation of a combined vaccine in children one to 11 years of age. A group of 232 healthy volunteers, one to 11 years of age at first vaccination, completed the study. Parents or guardians were asked to record specific local reactions and general symptoms that occurred up to three days following vaccination. Any other adverse event that occurred up to one month following vaccination was also recorded.
About 80 percent of participants reported symptoms following vaccination. Pain at the injection site was the most common local symptom, with redness and swelling being distant second and third symptoms. In participants younger than six years, fever was the most common general symptom, followed by loss of appetite. Fatigue was the most common general symptom in participants six years or older, followed by headache. Other generalized symptoms included influenza-like syndromes, gastroenteritis and bronchitis.
The immunogenicity analysis after eliminating participants found to be initially positive for anti-hepatitis A virus antibodies (anti-HAV) and/or hepatitis B surface antibodies (anti-HBs) demonstrated that after one month all but one participant had seroconverted for anti-HAV antibodies, with 100 percent seroconversion occurring at month 7, one month after the second injection. There was a continuous increase in anti-HBs seroconversion rates over time until month 6, when 93.9 percent of participants were seropositive and 78.2 percent of participants were considered seroprotected. One month after the second vaccination, at month 7, all children seroconverted for anti-HBs antibodies, with adequate levels of protection in 98.5 percent of participants.
The authors conclude that a two-dose vaccination course had high immunogenicity represented by high seroconversion rates and adequate antibody levels to impart 100 percent protection against hepatitis A and 98.5 percent protection against hepatitis B. A two-dose regimen for vaccination is likely to increase patient compliance with completion of the regimen and to reduce vaccination costs.