Clinical trial with inactivated hepatitis A vaccine and recommendations for its use.

OBJECTIVE--To compare the reactogenicity and immunogenicity of an inactivated hepatitis A vaccine in two different immunisation schedules. DESIGN--Randomised trial. SETTING--One London teaching hospital. SUBJECTS--104 healthy adult volunteers (71 men, 33 women aged 19-60). INTERVENTIONS--Hepatitis A vaccine to group 1 (54 volunteers) at 0, 1, and 2 months and to group 2 (50) at 0, 1, and 6 months. MAIN OUTCOME MEASURES--Symptoms at and after each dose; liver function, hepatitis A virus specific serum immune response; and responses in saliva and parotid fluid in immunised volunteers and subjects with natural immunity. RESULTS--The vaccine was well tolerated; 97% (96/99) and 100% of those immunised developed serum antibody after one and two doses of vaccine respectively. Geometric mean titres increased progressively after each dose and were significantly higher in men but not women in group 2 after the third dose (ratio between geometric mean titres 0.265, 95% confidence interval 0.18 to 0.39; p less than 0.001). At one year this group-sex interaction was absent; geometric mean titres for both sexes were significantly higher in group 2 (ratio 0.330, 0.227 to 0.478; p less than 0.0001). Antibody responses were not significantly different between the groups at two years. Compared with naturally infected subjects immunised volunteers developed poor or undetectable virus specific IgG and IgA responses in saliva and parotid fluid. CONCLUSIONS--The vaccine was safe and highly immunogenic, and the differences in the immune responses in saliva and parotid fluid are unlikely to affect its efficacy.