Biomedical subjects
Van Damme P
Publications and source records attributed to Van Damme P.
Safety and Immunogenicity of a High-Potency Inactivated Hepatitis A Vaccine.
Background: In recent years, several hepatitis A vaccines have been developed. We wished to evaluate the safety, reactogenicity, and immunogenicity of an inactivated hepatitis A vaccine, containing 1440 EI.U., and to monitor the kinetics of the antibodies monthly for the first year after administration of a single dose of vaccine. Methods: We conducted an open clinical trial, started in March 1992 and completed in July 1993, at two general hospitals and one pediatric hospital in Antwerp, Belgium, with 194 healthy adult healthcare volunteers. Each volunteer received a single dose hepatitis A vaccine, given intramuscularly at month 0 and a booster at month 12. We undertook serologic follow-up of antihepatitis A virus (antiHAV) antibodies and liver enzymes at day 15 and at months 1, 6, 9, 12, and 13. For a random subgroup of participants, blood samples were taken monthly. In addition, all participants noted local and general symptoms following administration of the vaccine. Results: This single dose vaccine was well-tolerated; 2 weeks after the vaccination, 80% of the participants had seroconverted (antiHAV antibodies >=20 mIU/mL); after 1 month, seroconversion reached 99% (geometric mean titer (GMT): 383 mIU/mL). One year after the single dose of vaccine, 94% still had antiHAV antibodies above 20 mIU/mL (GMT: 176 mIU/mL). One month after the booster dose, seroconversion was 100%, and GMT increased from 176 mIU/mL at month 12 to 4775 mIU/mL at month 13. Conclusions: The single dose hepatitis A vaccine is safe and highly immunogenic; it gives a rapid antibody production and a rapid increase of GMT. The persistence of protective antibodies until month 12 allows a booster at month 12. This schedule will easily fit into existing travel or occupational health vaccination schedules and will improve vaccination compliance.
Recommendations for Prevention of Hepatitis A Based on a Cost-Effectiveness Analysis.
Hepatitis A viral infection poses a substantial risk for travelers from low-endemic countries visiting high-endemic destinations. In this study, the general indications for the optimal prevention of hepatitis A are derived using a cost-effectiveness analysis based on the risk exposure determined by frequency and duration of travel as well as natural immunity. Three possible hepatitis A prevention strategies are compared to no prophylaxis: active immunization; an initial screening for HAV followed by active immunization of susceptible travelers; and passive immunization with immune globulins. Using a number of baseline assumptions, a scenario for travel from low- to high-endemic countries and an average travel duration and frequency rate, threshold values were obtained comparing active versus passive immunization. The study shows that, for travelers not expected to journey more than twice in a 10-year period, passive immunization is the most cost-effective prophylaxis for travel from both very-low or low-to-high endemic areas. For more frequent travel, vaccination is more cost effective, as well as for journeys of 6-months' duration or longer. As well, pretravel screening before vaccination was shown to be worthwhile, except when the probability of natural immunity is low. As the results indicate, the cost effectiveness of a strategy is related to several considerations: the prices of vaccine and screening tests, travel destinations and endemic conditions, frequency and duration of travel, and natural immunity. A decision-tree-based simulation model is helpful in determining the strategy to employ.