Table 3.

HBsAg and anti-HBc positive rates of participants at 20–31 years after primary vaccination.

Time after vaccination	No. detected	HBsAg		Anti-HBc
		No. positive	Positive rate (%)	No. positive	Positive rate (%)
20	43	0	0.00	1	2.33
21	74	0	0.00	1	1.35
22	50	1	2.00	3	6.00
23	55	0	0.00	0	0.00
24	35	0	0.00	1	2.86
25	58	0	0.00	3	5.17
26	68	0	0.00	4	5.88
27	84	0	0.00	4	4.76
28	104	1	0.96	8	7.69
29	158	2	1.27	11	6.96
30	179	1	0.56	15	8.38
31	41	1	2.43	5	12.20
total	949	6	0.63	56	5.90