TABLE 2.

Anti-HBs decay by enzyme immunoassays in children immunized and boosted with hepatitis B vaccine at ages 13 to 16 years

Vaccination groupa	Age (yr)
	13	14	15	16
Ia
No.	170	162	35	61
% with protective anti-HBs levels	15.3	14.8	25.7	19.7
GMT (mIU/ml)	1.4	0.9	1.2	0.9
Ib
No.	154	140	51	56
% with protective anti-HBs levels	43.5	38.6	43.1	35.7
GMT (mIU/ml)	7.2	5.7	6.3	4.5
II
No.	433	385	84	85
% with protective anti-HBs levels	78.5	73.2	73.8	60.0
GMT (mIU/ml)	32.9	26.6	22.3	18

^aIa, children who had anti-HBs levels <10 S/N at age 7 years and who did not receive any booster during the follow-up; Ib, children who had anti-HBs levels <10 S/N at age 7 years and who received boosters at age 7 years; II, children who had anti-HBs levels ≧10 S/N at age 7 years and who did not receive a booster vaccination during the follow-up.