Table 2.
Estimated Vaccine Effectiveness for Various Levels of Clinical Nontesting in a Simulated Group of 2000 ARI Outpatients* With the Overall Proportion Not Tested = 25% (C’)
| % Nontesting Variation Compared With Baselinea (v) | Vaccinated Influenza (+) (Cell a, n = 172) | Vaccinated Influenza (−) (Cell b, n = 1028) | Unvaccinated Influenza (+) (Cell c, n = 200) | Unvaccinated Influenza (−) (cell d, n = 600) | eVE Among Clinically Tested |
|---|---|---|---|---|---|
| Baselineb: 75% of All Patients Are Tested in All 4 Cells, 25% Not Tested = C’ | |||||
| Not tested N (%) | |||||
| 0% | 43 (25) | 257 (25) | 50 (25) | 150 (25) | 50% |
| Scenario 1b: Influenza-Negative Patients Tested Less Than Baseline | |||||
| 5% | 34 (20) | 270 (26) | 39 (20) | 157 (26) | 50% |
| 10% | 25 (15) | 282 (27) | 28 (15) | 165 (27) | 50% |
| 15% | 15 (9) | 295 (29) | 17 (9) | 173 (29) | 50% |
| Ceiling, 23% | 1 (0.6) | 315 (31) | 1 (0.6) | 183 (31) | 50% |
| Scenario 2b: Vaccinated Patients Tested Less Than Baseline | |||||
| 10% | 48 (28) | 282 (28) | 42 (21) | 128 (21) | 50% |
| 25% | 54 (31) | 321 (31) | 31 (16) | 94 (16) | 50% |
| 50% | 65 (38) | 385 (38) | 12 (6) | 38 (6) | 50% |
| Ceiling, 65% | 71 (41) | 424 (41) | 1 (0.5) | 4 (0.5) | 50% |
| Scenario 3b: Vaccinated Influenza-Positive Patients Tested Less Than Baseline | |||||
| 10% | 48 (28) | 254 (25) | 50 (25) | 149 (25) | 52% |
| 25% | 54 (31) | 251 (24) | 49 (24) | 146 (24) | 54% |
| 50% | 65 (38) | 245 (24) | 48 (24) | 143 (24) | 59% |
| 57% | 68 (39) | 243 (24) | 47 (24) | 142 (24) | 60% |
| Ceiling, 100% | 86 (50) | 233 (22) | 45 (22) | 136 (22) | 68% |
| Scenario 4b: Vaccinated Influenza-Negative Patients Tested Less Than Baseline | |||||
| 10% | 39 (23) | 282 (26) | 45 (23) | 134 (23) | 46% |
| 25% | 32 (19) | 321 (30) | 37 (19) | 110 (19) | 41% |
| 26% | 31 (18) | 324 (32) | 36 (18) | 109 (18) | 40% |
| 50% | 21 (12) | 385 (36) | 24 (12) | 71 (12) | 29% |
| Ceiling, 94% | 1 (0.6) | 498 (46) | 0 (0) | 1 (0.2) | 3% |
| Scenario 5b: Unvaccinated Influenza-Positive Patients Tested More Than Baseline | |||||
| 10% reduction | 43 (25) | 260 (25) | 45 (23) | 152 (25) | 52% |
| 25% reduction | 44 (26) | 264 (26) | 38 (19) | 154 (26) | 54% |
| 50% reduction | 46 (27) | 276 (27) | 17 (8) | 161 (27) | 58% |
| 67% reduction | 46 (27) | 276 (27) | 17 (8) | 161 (27) | 60% |
| Ceiling, 100% | 48 (28) | 286 (28) | 0 (0) | 167 (28) | 64% |
Abbreviations: ARI, acute respiratory infection; C’, the overall proportion not tested; eVE, estimated vaccine effectiveness; v, the additional change in proportion not tested in 1 or more cells.
*Overall percentage vaccinated is 60%, prevalence of infection in vaccinated patients is 25%, true vaccine effectiveness is 50%.
aRefers to changes in proportion of not-tested ARI patients in the targeted cells compared with the baseline scenario of 25% not tested in all cells.
bCells with targeted changes in nontesting are bolded.