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.