Rapid antibody response after vaccination with a virosomal hepatitis a vaccine.
BACKGROUND
This study was designed to assess the early antibody kinetics after a priming dose, and the extent of the antibody increase after a booster dose of an inactivated virosomal hepatitis A virus (HAV) vaccine (Epaxal).


METHODS
This was an open, uncontrolled study in 30 healthy subjects. The vaccine was injected intramuscularly on day 1 and month 12. Serum antibody titers were measured by ELISA on day 1 (pre dose) and at various time points thereafter until month 12 (pre-booster dose). After the booster dose, antibody titers were measured at various intervals until month 24. Neutralizing antibody titers were measured in 12 subjects a number of times during the 1st month by an antibody neutralization assay. Titers > or = 10 mIU/ml were considered seroprotective.


RESULTS
ELISA antibody titers showed a rapid increase post vaccination. By day 15, 96% of subjects were seroprotected, which increased to 100% by day 22 (n = 27 evaluable subjects, aged 18-43 years; 13 male, 14 female). All subjects achieved seroprotective HAV-neutralizing antibody titers by day 11 (n = 12). The booster vaccination at month 12 resulted in a strong response in all subjects, with a sustained anti-HAV antibody titer (1,155 mIU/ml) at month 24. Both the priming and booster doses were well tolerated.


CONCLUSIONS
Primary vaccination with this virosomal HAV vaccine is well tolerated and induces a rapid HAV-neutralizing antibody response resulting in seroprotection in all subjects within 10 days. In addition, the booster vaccination results in prolonged seroprotective antibody levels.
Ambrosch
F
F
Dept. of Specific Prophylaxis and Tropical Medicine, Institute of Pathophysiology, University of Vienna, Impfzentrum Nord, Austria. f.ambrosch@impfzentrum.at
Finkel
B
B
Herzog
C
C
Koren
A
A
Kollaritsch
H
H
D000293:Adolescent; D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006506:Hepatitis A / Q000517:prevention & control*; D035922:Hepatitis A Antibodies / Q000097:blood*; D022362:Hepatitis A Vaccines / Q000008:administration & dosage* / Q000276:immunology; D017957:Hepatitis A Virus, Human / Q000276:immunology*; D006801:Humans; D007117:Immunization, Secondary; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D013997:Time Factors; D014611:Vaccination; D022721:Vaccines, Virosome / Q000008:administration & dosage / Q000276:immunology
D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines; D022721:Vaccines, Virosome