TABLE 3.
Estimated titers for 50% protection against A/H3N2 influenza illness
| Case definitiona (n) | Titer for 50% protectionb (95% CI) |
||||
|---|---|---|---|---|---|
| HAI, vaccine virus (n = 5,752) | HAI, circulating virus (n = 673) | NT, vaccine virus (n = 675) | NT, circulating virus (n = 675) | N2 ELLA (n = 675) | |
| Laboratory-confirmed influenza associated with RI (n = 152/123) | 359 (95.8, 574) | 44.7 (17.4, 62.1) | 180 (17.2, 368) | — | 93.0 (17.1, 184) |
| Laboratory-confirmed influenza associated with PD-ILI (n = 121/98) | 285 (69.6, 500) | 40.6 (10.5, 58.7) | 141 (68.9, 238) | — | 16.8 (11.3, 115) |
| Laboratory-confirmed influenza associated with CDC-ILI (n = 52/48) | 265 (131, 408) | 23.7 (7.4, 52.7) | — | 219 (82.9, 365) | 16.8 (9.0, 103) |
| Antigenically similar influenza associated with RI (n = 37/34) | 437 (99.7, 1347) | 36.2 (12.3, 93.0) | — | 47.7 (25.8, 1163) | 34.8 (18.7, 38.8) |
| Antigenically similar influenza associated with PD-ILI (n = 30/28) | 399 (83.2, 1273) | 22.4 (9.0, 44.8) | — | 47.3 (21.7, 696) | 33.5 (14.3, 49.4) |
| Antigenically similar influenza associated with CDC-ILI (n = 18/17) | 203 (97.8, 302) | 23.7 (12.0, 52.7) | — | 196 (60.2, 257) | 17.6 (10.3, 27.3) |
a
n indicates the number of cases. The first number is for the HAI vaccine virus assay, the second is for the other assays.
b
—, goodness of fit of <0.5.