<qa>  What is the time period for a blood sample to be taken?If a subject has become seronegative for anti-HAV antibodies during any of the long-term blood sampling time point i.e. Months 138, 150, 162, 174,186, 198, 210, 222, 234 and 246, he she will be offered an additional vaccine dose. A blood sample will be taken on the day of the additional vaccination 14 days and one month after additional vaccination to evaluate the immune response following this vaccination. 