| Value | Category | Cases | |
|---|---|---|---|
| -1 | Missing | 2 |
0.1%
|
| 0 | Not at all effective | 181 |
7.5%
|
| 1 | Not very effective | 346 |
14.4%
|
| 2 | Somewhat effective | 563 |
23.4%
|
| 3 | Very effective | 1091 |
45.3%
|
| 9 | Don't know | 224 |
9.3%
|
| 998 | Refused | 0 |
0%
|