Seventeen-year antibody persistence in adults primed with two doses of an inactivated hepatitis A vaccine

Figures & data

Table 1. Number of subjects included in the LT-ATP cohort at Year 17 with reasons for elimination

	Study A (0, 6 mo)	Study B (0, 12 mo)
	Number of subjects	Number of subjects
No. of subjects returning for follow-up at Year 17	63	124
No. of subjects eliminated with reasons
Eliminated at a previous time point:
- Concomitant administration of vaccine forbidden in the protocol	1	2
- Non-compliance with blood sampling schedule	8	7
- Protocol violation linked to inclusion/exclusion criteria	2	-
- Non-compliance with vaccination schedule	1	-
- Biochemistry, hematology and other laboratory values outside range before vaccination	-	1
- Abnormal serological evolution*	6	21
Eliminated at Year 17 time point:
- Abnormal serological evolution*	-	2
No. of subjects included in the LT-ATP cohort for immunogenicity at Year 17	45	91

* Abnormal serological evolution was defined as at least a 2-fold increase in anti-HAV antibody concentration when the antibody concentration at the reference time-point was ≥ 100mIU/ml or at least a 4-fold increase in antibody concentration when the antibody concentration at the reference time-point was < 100mIU/ml.

Table 2. Percentage of subjects seropositive for anti-HAV antibodies at each yearly follow-up time point up to 17 y (Long-term Total cohort and LT ATP cohort)

	Long-term total cohort				LT-ATP cohort
Time points	N	Study A (0, 6 mo)	N	Study B (0, 12 mo)	N	Study A (0, 6 mo)	N	Study B (0, 12 mo)
		% (95% CI)		% (95% CI)		% (95% CI)		% (95% CI)
Year 2	70	100 (94.9;100)	166	99.4 (96.7;100)	53	100 (93.3;100)	137	99.3 (96.0;100)
Year 3	74	100 (95.1;100)	155	99.4 (96.5;100)	55	100 (93.5;100)	133	99.2 (95.9;100)
Year 4	67	100 (94.6;100)	152	99.3 (96.4;100)	50	100 (92.9;100)	126	99.2 (95.7;100)
Year 5	68	100 (94.7;100)	150	99.3 (96.3;100)	50	100 (92.9;100)	126	99.2 (95.7;100)
Year 6	61	100 (94.1;100)	141	99.3 (96.1;100)	46	100 (92.3;100)	119	99.2 (95.4;100)
Year 7	77	98.7 (93.0;100)	142	97.2 (92.9;99.2)	55	100 (93.5;100)	119	96.6 (91.6;99.1)
Year 8	59	100 (93.9;100)	127	99.2 (95.7;100)	49	100 (92.7;100)	109	99.1 (95.0;100)
Year 9	55	100 (93.5;100)	116	99.1 (95.3;100)	41	100 (91.4;100)	98	99.0 (94.4;100)
Year 10	50	100 (92.9;100)	112	99.1 (95.1;100)	40	100 (91.2;100)	86	100 (95.8;100)
Year 11	58	100 (93.8;100)	101	98.0 (93.0;99.8)	43	100 (91.8;100)	79	97.5 (91.2;99.7)
Year 11*	64	98.4 (91.6;100)	107	97.2 (92.0;99.4)	46	100 (92.3;100)	85	96.5 (90.0;99.3)
Year 12	60	100 (94.0;100)	117	97.4 (92.7;99.5)	42	100 (91.6;100)	93	96.8 (90.9;99.3)
Year 13	71	100 (94.9;100)	127	97.6 (93.3;99.5)	50	100 (92.9;100)	101	97.0 (91.6;99.4)
Year 14	66	97.0 (89.5;99.6)	127	98.4 (94.4;99.8)	46	100 (92.3;100)	102	98.0 (93.1;99.8)
Year 15	62	100 (94.2;100)	128	97.7 (93.3;99.5)	41	100 (91.4;100)	98	96.9 (91.3;99.4)
Year 16	78	97.4 (91.0;99.7)	135	99.3 (95.9;100)	53	100 (93.3;100)	101	96.0 (90.2;98.9)
Year 17	63	100 (94.3;100)	124	100 (97.1;100)	45	100 (92.1;100)	91	96.7 (90.7;99.3)

N, Number of subjects with available results; CI, Confidence Interval; *Serum samples up to Year 11 were tested with ELISA kits, while serum samples from Years 12 to 17 were tested with EIA kits. Blood samples at Year 11 were re-tested with the new assay kit and results were compared with the previous assay kit. Anti-HAV seropositivity cut-offs: (a) Up to Year 11: ≥ 20 mIU/ml; (b) Year 12 to Year 17: ≥ 15 mIU/ml.

Figure 1. Evolution of anti-HAV antibody geometric mean concentration across the yearly follow-up time points. *Serum samples up to Year 11 were tested with ELISA kits, while serum samples from Years 12 to 17 were tested with EIA kits. Blood samples at Year 11 were re-tested with the new assay kit and results were compared with the previous assay kit. Anti-HAV seropositivity cut-offs: Up to Year 11: ≥ 20 mIU/ml; Year 12 to Year 17: ≥ 15 mIU/ml