Table 5.
Bias of vaccine effectiveness (VE) estimates under assumptions A1, A3 for various values of ρβ*
| Comparison | ρβ = 0·5 | ρβ = 1·0 | ρβ = 2·0 | |||
|---|---|---|---|---|---|---|
| VEA | VEB | VEA | VEB | VEA | VEB | |
| 1 | −0·22 | −0·09 | 0·00 | −0·10 | 0·11 | −0·13 |
| 2 | −0·21 | −0·09 | 0·00 | −0·10 | 0·11 | −0·13 |
| 3 | −0·43 | −0·17 | 0·00 | −0·20 | 0·21 | −0·27 |
| 4 | −0·31 | −0·12 | 0·00 | −0·15 | 0·16 | −0·20 |
| 5 | −0·09 | −0·04 | 0·00 | −0·04 | 0·05 | −0·06 |
| 6 | −0·25 | −0·10 | 0·00 | −0·12 | 0·12 | −0·15 |
| 7 | −0·45 | −0·19 | 0·00 | −0·22 | 0·23 | −0·28 |
| 8 | −0·22 | −0·09 | 0·00 | −0·11 | 0·11 | −0·13 |
| 9 | −0·78 | −0·36 | 0·00 | −0·39 | 0·39 | −0·45 |
| 10 | −0·31 | −0·13 | 0·00 | −0·14 | 0·15 | −0·17 |
| 11 | −0·37 | −0·16 | 0·00 | −0·17 | 0·18 | −0·21 |
| 12 | −0·51 | −0·20 | 0·00 | −0·24 | 0·25 | −0·35 |
| 13 | −0·51 | −0·22 | 0·00 | −0·25 | 0·25 | −0·33 |
| 14 | −0·25 | −0·07 | 0·00 | −0·11 | 0·12 | −0·21 |
| Average bias | −0·35 | −0·14 | 0·00 | −0·17 | 0·18 | −0·22 |
| Avg absolute bias | 0·35 | 0·14 | 0·00 | 0·17 | 0·18 | 0·22 |
| Max abs bias | 0·78 | 0·36 | 0·00 | 0·39 | 0·39 | 0·45 |
*
ρβ = β1/β0, the ratio of the probabilities of a non-influenza acute respiratory illness (ARI) in vaccinees and non-vaccinees. We assume that the diagnostic test has perfect sensitivity and specificity and that the vaccination-related ratios of probabilities of seeking medical care for ARI are homogeneous, i.e. ρδ1 = ρδ2. VEA and VEB are the VE estimates from test-negative design and case-control design studies, respectively. The table's rows correspond to the comparisons of vaccinated and unvaccinated randomized clinical trial participants (see Table A1 in the Supplementary Appendix).