Table 1.
Seroprevalence of influenza A and B virus-specific IgG antibodies as function of age
| Age (years) | Influenza A | Influenza B | ||||
|---|---|---|---|---|---|---|
| Positive | Equivocal | Negative | Positive | Equivocal | Negative | |
| <3 | 13.0 (9) | 5.8 (4) | 81.1 (56) | 14.5 (10) | 5.8 (4) | 79.7 (55) |
| 3–4 | 9.7 (6) | 6.4 (4) | 83.9 (52) | 25.8 (16) | 4.8 (3) | 69.3 (43) |
| 4–5 | 14.9 (7) | 8.5 (4) | 76.6 (36) | 27.7 (13) | 10.6 (5) | 61.7 (29) |
| 5–6 | 18.7 (9) | 6.2 (3) | 75.0 (36) | 33.3 (16) | 14.6 (7) | 52.1 (25) |
| 6–12.5 | 24.1 (14) | 10.3 (6) | 65.5 (38) | 58.6 (34) | 13.8 (8) | 27.6 (16) |
| All | 15.8 (45) | 7.4 (21) | 76.7 (218) | 31.3 (89) | 9.5 (27) | 59.1 (168) |
Values are percent (n). Serologic studies were missing in some patients due to inadequate serum