Figure 1Comparison of antibody titers obtained using different tests in children who had completed a primary immunization schedule with mouse brain inactivated (A; n = 15) or live attenuated vaccines (B; n = 14). The PRNT and HI antibody titers ranged from 1:10 to 1:2560, whereas the IFA antibody titers started from 1:16 in two-fold serial dilutions. Test values: PRNT50% titers (closed boxes), HI titers (closed circles), IFA titers (open circles). Negative results (i.e., antibody titers less than 1:10 or 1:16) are not shown in the plots. 1/x = serum dilution factor (i.e., 80 or 160). HI = hemagglutination inhibition test; IFA = indirect immunofluorescence assay; PRNT = plaque reduction neutralization test.
Table 1Characteristics of the 29 children enrolled in the study.
Characteristics |
Group
|
Total |
Inactivated vaccine |
Live vaccine |
Number of children |
15 |
14 |
29 |
Number of doses in primary schedule |
3 |
2 |
– |
Mean (range) age at time of first dose (mo) |
16.4 (10.4–24.2) |
14.7 (11.9–24.3) |
15.6 (10.4–24.3) |
Mean (range) age at time of last dose (mo) |
31 (19.6–67.7)a
|
24.9 (18.4–31.6) |
28 (18.4–67.7) |
Interval between sampling and last dose (mo) |
27.9 (3.2–47.0) |
21.3 (3.0–47.1) |
24.7 (3.0–47.1) |
Table 2Rates of antibody detection obtained by four serological tests in children vaccinated for Japanese encephalitis.
Test |
Inactivated vaccine group (n = 15)
|
Live attenuated vaccine group (n = 14)
|
No. (%) positive |
GMT |
No. (%) positive |
GMT |
PRNT |
15 (100) |
1:292 |
14 (100) |
1:195 |
HI |
13 (86.7) |
1:20 |
10 (71.4) |
1:17 |
IFA (IgG) |
8 (53.3) |
1:99 |
5 (35.7) |
1:111 |
IFA (IgM) |
0 |
– |
0 |
– |
ELISA (IgG) |
0 |
– |
0 |
– |
ELISA (IgM) |
0 |
– |
0 |
– |