Table 3.
Change in cost-effectiveness analysis value determinations when herd immunity effects are incorporated
| All studies, n (%) | Pneumococcal vaccine studies, n (%) | |
|---|---|---|
| Number of studies reported ICERs with and without HI effectsa | 16 (of 44 studies) | 8 (of 16 studies) |
| Number of ICERs recalculated with/without herd immunity effectsb | 48 (of 140 ICERs) | 24 (of 48 ICERs) |
| $/QALY | 21 (44) | 18 (75) |
| $/DALY | 27 (56) | 6 (25) |
| Where herd immunity effects included | ||
| Base case | 25 (52) | 7 (29) |
| Sensitivity analysis | 24 (50) | 18 (75) |
| Both | 1 (2) | 1 (4) |
| Change in ICER after adding herd immunity effects | ||
| Increase | 0 (0) | 0 (0) |
| Decrease | 48 (100) | 24 (100) |
| No change | 0 (0) | 0 (0) |
| Including HI reduced the ICER enough to cross the following thresholdsc | ||
| $/DALY | ||
| Cost-saving threshold | 2 (7) | 1 (17) |
| 1 × GDP threshold | 10 (37) | 0 (0) |
| 3 × GDP threshold | 8 (30) | 2 (33) |
| Did not cross any threshold | 11 (41) | 3 (50) |
| $/QALY | ||
| Cost-saving threshold | 4 (19) | 4 (22) |
| 1 × GDP threshold | 6 (25) | 6 (33) |
| 3 × GDP threshold | 0 (0) | 0 (0) |
| Did not cross any threshold | 17 (81) | 13 (72) |
ICER incremental cost-effectiveness ratio, QALY quality-adjusted life-year, DALY disability-adjusted life-year, HI herd immunity, GDP gross domestic production
aICERs with and without HI effects were directly reported or allowed for recalculation of ICERs with available data
bRecalculated ICERs refer to a pair of ICERs from the same study, one that includes and the other without herd immunity effects
cNot mutually exclusive: including herd immunity may cause the ICER results to cross more than one threshold (e.g., ICER results changed from dominated to below 1 × GDP threshold, the results were counted in both 1 × GDP threshold and 3 × GDP threshold categories)