Table 2. Vaccine Effectiveness against Delta Variant–Related Hospitalization among Persons in England Who Received Two Doses of ChAdOx1-S or BNT162b2 Vaccine, According to Weeks since Receipt of the Second Dose.*.
| Vaccine, Age Group, and Subgroup | Vaccine Effectiveness (95% CI) | ||||
|---|---|---|---|---|---|
| 1 Wk | 2–9 Wk | 10–14 Wk | 15–19 Wk | ≥20 Wk | |
| percent | |||||
| ChAdOx1-S | |||||
| ≥16 Yr | 94.0 (91.3–95.8) | 95.2 (94.7–95.7) | 92.1 (91.3–92.7) | 87.4 (86.1–88.6) | 80.0 (76.8–82.7) |
| ≥65 Yr | |||||
| All | 91.5 (37.0–98.9) | 91.7 (88.8–93.9) | 90.1 (87.7–92.0) | 85.8 (82.7–88.4) | 81.8 (76.6–85.9) |
| Clinically extremely vulnerable group | |||||
| Yes | 100 (1 case, 290 controls) | 78.6 (63.7–87.4) | 79.2 (68.7–86.2) | 75.1 (63.3–83.1) | 66.5 (47.9–78.4) |
| No | 100 (1 case, 1221 controls) | 94.2 (91.5–96.1) | 92.4 (90.1–94.1) | 88.0 (84.8–90.5) | 85.9 (80.6–89.8) |
| 40–64 Yr | |||||
| All | 94.5 (91.8–96.4) | 96.2 (95.7–96.6) | 93.2 (92.4–94.0) | 89.9 (88.1–91.4) | 79.1 (70.3–85.3) |
| Clinical risk or clinically extremely vulnerable group | |||||
| Yes | 94.6 (86.9–97.8) | 93.7 (92.4–94.8) | 90.4 (88.7–91.8) | 86.6 (83.7–89.0) | 76.9 (65.2–84.6) |
| No | 94.7 (91.7–96.7) | 97.5 (97.0–98.0) | 95.6 (94.6–96.4) | 94.4 (92.1–96.0) | 74.6 (48.2–87.6) |
| BNT162b2 | |||||
| ≥16 Yr | 99.4 (97.7–99.9) | 98.7 (98.3–99.0) | 96.8 (96.3–97.3) | 94.9 (94.1–95.5) | 91.7 (90.2–93.0) |
| ≥65 Yr | |||||
| All | 100 (0 cases, 912 controls) | 98.0 (95.9–99.1) | 95.8 (94.4–96.9) | 93.4 (91.6–94.7) | 90.5 (87.6–92.7) |
| Clinically extremely vulnerable group | |||||
| Yes | 100 (0 cases, 173 controls) | 95.7 (85.4–98.7) | 89.3 (82.5–93.5) | 84.6 (76.8–89.8) | 78.6 (66.6–86.2) |
| No | 100 (0 cases, 739 controls) | 98.5 (96.2–99.4) | 97.4 (96.1–98.2) | 95.7 (94.2–96.8) | 94.3 (91.8–96.0) |
| 40–64 Yr | |||||
| All | 100 (0 cases, 2798 controls) | 98.6 (97.9–99.1) | 97.7 (96.9–98.3) | 96.5 (95.3–97.4) | 93.8 (87.5–96.9) |
| Clinical risk or clinically extremely vulnerable group | |||||
| Yes | 100 (0 cases, 1113 controls) | 98.2 (97.1–98.8) | 96.8 (95.6–97.6) | 95.8 (94.2–96.9) | 93.1 (84.3–96.9) |
| No | 100 (0 cases, 1685 controls) | 99.1 (97.7–99.7) | 99.4 (97.6–99.9) | 97.3 (94.2–98.7) | 93.4 (73.4–98.4) |
| 16–39 Yr | 99.2 (96.9–99.8) | 99.2 (98.3–99.6) | 100 (0 cases, 2584 controls) | — | — |
*
When vaccine effectiveness was calculated as 100%, the numbers of total case and control participants are shown in parentheses. Persons in a clinical risk group had a broad range of chronic conditions as described in the Green Book.15 The clinically extremely vulnerable group included persons who were considered to be at highest risk for severe Covid-19.16