doi:10.1007/s11908-009-0027-1. 6 months, peaked at 7 months to 3 years, and remained high at 4 to 6 6 years. The antibody titers started to decrease after 6 years and were the lowest in the 21- to 30-12 months group. The geometric mean titers (GMTs) of T- and B-cell combined antigenic Continue Reading