Table 4.
Absolute risk reductions and numbers needed to be vaccinated (NNVs) in geographical regions with different baseline risks, population-based data Hospitalisations
| A. County or state | B. Active cases per 100 000 population* | C. Calculated hospitalisations per 100 000 (estimated at 6.86% of cases) (B×6.86%)† | D. Calculated hospitalisations per 100 000 (expressed as %)=baseline risk (C/100 000) (%) | E. Calculated risk of hospitalisation after vaccine with 95% or 66% effectiveness (RRR 95% or 66%) (D×5% or 34%) (%)‡ | F. Absolute risk reduction (D−E) (%) | G. Number needed to be vaccinated |
| May 2021 | ||||||
| Los Angeles, California | 270.43 | 18.55 | 0.02 | 0.00 | 0.02 (0.00 to 0.03) | 5000 (3464 to 8983) |
| Hampshire, Massachusetts | 251 | 17.22 | 0.02 | 0.00 | 0.02 (0.00 to 0.03) | 5000 (3464 to 8983) |
| Putnam, New York | 164 | 11.25 | 0.01 | 0.00 | 0.01 (0.00 to 0.02) | 10 000 (6146 to 26 815) |
| De Baca, New Mexico | 1124.74 | 77.16 | 0.08 | 0.01 | 0.07 (0.05 to 0.09) | 1429 (1126 to 1953) |
| McKinley, New Mexico | 730.89 | 50.14 | 0.05 | 0.00 | 0.05 (0.04 to 0.06) | 2000 (1562 to 2779) |
| Catron, New Mexico | 80.95 | 5.55 | 0.01 | 0.00 | 0.01 (0.00 to 0.02) | 10 000 (6146 to 26 815) |
| Ladakh state, India | 6250 | 428.75 | 0.43 | 0.02 | 0.41 (0.37 to 0.45) | 244 (221 to 272) |
| Uttar Pradesh state, India | 833 | 57.14 | 0.06 | 0.00 | 0.06 (0.05 to 0.08) | 1667 (1327 to 2239) |
| Kerala state, India | 7143 | 490.01 | 0.49 | 0.02 | 0.47 (0.43 to 0.52) | 213 (194 to 235) |
| September 2021 | ||||||
| Los Angeles, California | 472 | 32.38 | 0.03 | 0.01 | 0.02 (0.01 to 0.03) | 5000 (3073 to 13 406) |
| Hampshire, Massachusetts | 228 | 15.64 | 0.02 | 0.01 | 0.01 (0.00 to 0.01) | 10000 (4794 to –116 171) |
| Putnam, New York | 341 | 23.39 | 0.02 | 0.01 | 0.01 (0.00 to 0.01) | 10000 (4794 to –116 171) |
| De Baca, New Mexico | 409 | 28.06 | 0.03 | 0.01 | 0.02 (0.01 to 0.03) | 5000 (3073 to 13 406) |
| McKinley, New Mexico | 517 | 35.47 | 0.04 | 0.01 | 0.03 (0.02 to 0.04) | 3333 (2272 to 6258) |
| Catron, New Mexico | 405 | 27.78 | 0.03 | 0.01 | 0.02 (0.01 to 0.03) | 5000 (3073 to 13 406) |
| Ladakh state, India | 28 | 1.92 | 0.00 | 0.00 | 0 (0.00 to 0.00) | ∞ |
| Uttar Pradesh state, India | 14 | 0.96 | 0.00 | 0.00 | 0 (0.00 to 0.00) | ∞ |
| Kerala state, India | 1204 | 82.59 | 0.08 | 0.03 | 0.05 (0.03 to 0.07) | 2000 (1413 to 3424) |
95% CIs shown in parentheses. CIs that include negative numbers or infinity indicate non-significant differences in harm between the intervention and control groups. Such intervals do not necessarily include the point estimates and reflect a range from beneficial to harmful effects of the intervention.28
*Sources: Johns Hopkins dashboard (https://www.arcgis.com/apps/MapSeries/index.html?appid=ad46e587a9134fcdb43ff54c16f8c39b) (accessed 5 September 2021); New York Times dashboard (https://www.nytimes.com/interactive/2020/world/asia/india-coronavirus-cases.html)(accessed 23 May 2021 and 5 September 2021).
†Estimate of percentage of infections that require hospitalisation (infection hospitalisation rate (IHR)), based on the upper limit of 6.86% in published research.40 41 Further explanation in text. Online supplement table 4 presents a sensitivity analysis assuming an IHR based on the lower limit of 2.10% in published research.
‡Reported effectiveness of the most effective vaccines (RRR) decreased from the range of 95% during May 2021 to the range of 66% during September 2021, based mainly on the emergence of the Delta variant.57
RRR, relative risk reduction.