Table 2. Vaccine Efficacy of ZF2001 against Covid-19 According to Analysis Groups.
| Efficacy Analysis | At First Data Cutoff: June 30, 2021 | At Second Data Cutoff: Dec. 15, 2021 | ||||||
|---|---|---|---|---|---|---|---|---|
| Total Cases | ZF2001 | Placebo | Vaccine Efficacy (95% CI) |
Total Cases | ZF2001 | Placebo | Vaccine Efficacy (95% CI) |
|
| no. | no. of cases/no. at risk | % | no. | no. of cases/no. at risk | % | |||
| Analyses in the modified full analysis set * | ||||||||
| Primary end point: symptomatic Covid-19 occurring ≥7 days after the third dose | 224 | 36/7359 | 188/7322 | 81.4 (73.3 to 87.3) | 738 | 158/12,625 | 580/12,568 | 75.7 (71.0 to 79.8) |
| Secondary end point: severe-to-critical Covid-19 occurring ≥7 days after the third dose | 14 | 1/7359 | 13/7322 | 92.9 (52.4 to 99.8) | 49 | 6/12,656 | 43/12,568 | 87.6 (70.6 to 95.7) |
| Secondary end-point component: Covid-19–related death occurring ≥7 days after the third dose | 5 | 0/7359 | 5/7322 | 100 (−8.4 to 100) | 14 | 2/12,656 | 12/12,568 | 86.5 (38.9 to 98.5) |
| Subgroup analyses in the modified full analysis set | ||||||||
| Analysis according to age | ||||||||
| 18–59 yr | 216 | 35/7153 | 181/7111 | 81.2 (72.8 to 87.3) | 710 | 150/11,921 | 560/11,846 | 76.0 (71.2 to 80.1) |
| ≥60 yr | 8 | 1/206 | 7/211 | 87.6 (2.5 to 99.7) | 28 | 8/704 | 20/722 | 67.6 (21.9 to 87.8) |
| Analysis according to country† | ||||||||
| Uzbekistan | 53 | 7/3185 | 46/3180 | 84.8 (66.2 to 94.2) | 191 | 35/3226 | 156/3221 | 80.2 (71.3 to 86.7) |
| Indonesia | 159 | 28/1908 | 131/1895 | 79.4 (68.9 to 86.9) | 352 | 77/1927 | 275/1902 | 76.0 (68.9 to 81.6) |
| Ecuador | 12 | 1/1323 | 11/1293 | 91.2 (39.5 to 99.8) | 130 | 33/2280 | 97/2249 | 67.6 (51.4 to 78.9) |
| Pakistan | 0 | 0/943 | 0/954 | NA | 65 | 13/5192 | 52/5196 | 75.1 (53.7 to 87.6) |
| Analysis according to race | ||||||||
| Asian | 211 | 35/5997 | 176/5964 | 80.7 (72.1 to 87.0) | 601 | 124/10,303 | 477/10,252 | 77.2 (72.2 to 81.5) |
| Other race | 13 | 1/1362 | 12/1358 | 91.7 (43.4 to 99.8) | 137 | 34/2322 | 103/2316 | 68.2 (52.8 to 79.1) |
| Analysis according to coexisting conditions that were risk factors for severe Covid-19 | ||||||||
| Cardiovascular disease | 12 | 1/203 | 11/242 | 93.1 (45.4 to 99.9) | 38 | 11/401 | 27/454 | 64.0 (20.2 to 84.9) |
| Diabetes | 5 | 1/88 | 4/95 | 31.7 (−1264.8 to 98.9) | 17 | 5/279 | 12/299 | 55.4 (−60.4 to 90.1) |
| Chronic lung disease | 3 | 1/42 | 2/27 | 74.0 (−435.3 to 99.6) | 7 | 2/54 | 5/43 | 86.7 (−13.9 to 99.0) |
| Severe obesity | 1 | 0/8 | 1/11 | 100 (−3275.7 to 100) | 1 | 0/9 | 1/14 | 100 (−4353.8 to 100) |
| Any of the above | 19 | 3/308 | 16/344 | 84.4 (41.9 to 97.2) | 58 | 18/661 | 40/716 | 61.6 (29.5 to 79.9) |
| Analysis according to SARS-CoV-2 variant‡ | ||||||||
| B.1.617.2, AY.4, AY.6, or AY.12 (delta) | 130 | 21/7359 | 109/7322 | 81.4 (70.1 to 88.9) | 454 | 96/12,625 | 358/12,568 | 76.1 (70.0 to 81.2) |
| B.1.1.7 (alpha) | 29 | 2/7359 | 27/7322 | 92.7 (70.9 to 99.2) | 35 | 4/12,625 | 31/12,568 | 88.3 (66.8 to 97.0) |
| B.1.617.1 (kappa) or B.1.617.3 | 15 | 2/7359 | 13/7322 | 84.8 (32.9 to 98.3) | 68 | 15/12,625 | 53/12,568 | 75.2 (55.3 to 87.0) |
| Other variants or not identified§ | 50 | 11/7359 | 38/7322 | 71.3 (42.7 to 86.8) | 181 | 43/12,625 | 138/12,568 | 71.9 (60.1 to 80.5) |
| Analyses in the full analysis set ¶ | ||||||||
| Symptomatic Covid-19 since the first dose | 663 | 249/13,669 | 414/13,664 | 40.2 (29.9 to 49.1) | 1255 | 405/13,909 | 850/13,899 | 55.4 (49.7 to 60.4) |
| Severe-to-critical Covid-19 since the first dose | 59 | 26/13,669 | 33/13,664 | 21.6 (−35.1 to 55.0) | 101 | 36/13,909 | 65/13,899 | 47.4 (19.8 to 66.0) |
| Covid-19–related death since the first dose | 6 | 0 | 6/13,664 | 100 (15.2 to 100) | 18 | 4/13,909 | 14/13,898 | 75.5 (21.5 to 94.1) |
The modified full analysis set for efficacy included all the participants who had undergone randomization and completed the three-dose regimen (additional exclusion criteria are listed in Table S3 in the Supplementary Appendix). Participants who had received the incorrect trial regimen were included in the analysis according to their trial-group assignment on the basis of the intention-to-treat principle. Covid-19 denotes coronavirus disease 2019, and NA not applicable.
Lot 1 vaccine was used in the Uzbekistan cohort, and lot 2 vaccine was used in the other countries.
Vaccine efficacy against each severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant was determined on the basis of symptomatic cases in the modified full analysis set for efficacy that were confirmed on real-time PCR assay and had SARS-CoV-2 genotyped with nasopharyngeal swabs.
Nasopharyngeal swabs with a cycle threshold value of 30 or more were not genotyped. We were able to retrieve sequences or genotypes from 185 case samples in the short-term follow-up and 626 case samples in the long-term follow-up. Shown are the efficacies against three major variants. The other 11 confirmed SARS-CoV-2 variants identified in the short-term follow-up and 69 in the long-term follow-up are shown in Table S14.
The full analysis set for efficacy included all the participants who had undergone randomization and received at least one dose of vaccine or placebo. The full analysis set was used to evaluate protective efficacy after the first dose. The end-point cases were counted since the receipt of the first dose of vaccine or placebo. The current analysis did not include data from 7 participants who had a positive test for IgG or IgM antibodies or SARS-CoV-2 antigen or had a positive real-time PCR assay at baseline and those who had not yet completed at least one case-surveillance follow-up visit (121 patients at the first data cutoff date and 27 at the second data cutoff date).