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. 2012 Mar 16;7(3):e33392. doi: 10.1371/journal.pone.0033392

Table 2. Epidemiological study of neutralizing antibodies in the general population in China.

VTT NAb titera, num (%) Total num (%)
<30 (Neg) 30–100 >100 >30 (Pos)
Age, years Num
18–30 222 222 (100%) 0 (0%) 0 (0%) 0 (0%)
31–40 162 153 (94.5%) 8 (4.9%) 1 (0.6%) 9 (5.5%)
41–56 116 104 (89.7%) 10 (8.6%) 2 (1.7%) 12 (10.3%)b
Total 500 479 (95.8%) 18 (3.6%) 3 (0.6%) 21 (4.2%)
Sex
Male 278 266 (95.7%) 10 (3.6%) 2 (0.7%) 12 (4.3%)
Female 222 213 (96.0%) 8 (3.6%) 1 (0.4%) 9 (4.0%)
Total 500 479 (95.8%) 18 (3.6%) 3 (0.6%) 21 (4.2%)
Site
Beijing 300 290 (96.6%) 8 (2.7%) 2 (0.7%) 10 (3.3%)
Anhui 200 189 (94.5%) 10 (5.0%) 1 (0.5%) 11 (5.5%)
Total 500 479 (95.8%) 18 (3.6%) 3 (0.6%) 21 (4.2%)
a

The titers (vaccinia-neutralizing activity) were determined using the neutralization assay described in Table 1. Arbitrary intervals were established as a qualitative reference for the potency of a determined serum, i.e., negative (<30), low (30–100), and high (>100).

b

the percentage of positive VTT NAbs increased with age.