Table 3.
Effect of vaccine on cases of Ebola virus disease in different study populations
|
All clusters* |
Randomised clusters† |
|||||||
|---|---|---|---|---|---|---|---|---|
| 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
|
| All vaccinated in immediate (group A) vs all contacts and contacts of contacts in delayed plus all never-vaccinated in immediate or non-randomised (group B) | All vaccinated in immediate (group A) vs all eligible in delayed plus all eligible never-vaccinated in immediate (group B) | All contacts and contacts of contacts in immediate (group A) vs delayed (group B) | All vaccinated in immediate (group A) vs all eligible never vaccinated in immediate (group B) | All vaccinated in immediate (group A) vs all eligible and consented on day 0 visit in delayed (group B) | All vaccinated in immediate (group A) vs all eligible in delayed (group B) | All eligible in immediate (group A) vs all eligible delayed (group B) | All contacts and contacts of contacts in immediate (group A) vs all contacts and contacts of contacts in delayed (group B) | |
| Group A | ||||||||
| Number of individuals (clusters) | 3775 (70) | 3775 (70) | 7241 (70) | 3775 (70) | 2108 (51) | 2108 (51) | 3212 (51) | 4513 (51) |
| Cases of Ebola virus disease (clusters affected) | 0 (0) | 0 (0) | 12 (7) | 0 (0) | 0 (0) | 0 (0) | 7 (4) | 10 (5) |
| Attack rate | 0% | 0% | 0·17% | 0% | 0% | 0% | 0·22% | 0·22% |
| Group B | ||||||||
| Number of individuals (clusters) | 7995 (116) | 4507 (104) | 4529 (47) | 1432 (57) | 1429 (46) | 3075 (47) | 3075 (47) | 4529 (47) |
| Cases of Ebola virus disease (clusters affected) | 34 (15) | 23 (11) | 22 (8) | 7 (4) | 10 (4) | 16 (7) | 16 (7) | 22 (8) |
| Attack rate | 0·43% | 0·51% | 0·49% | 0·49% | 0·7% | 0·52% | 0·52% | 0·49% |
| Vaccine effect | ||||||||
| Vaccine efficacy/effectiveness‡ (%, 95% CI) | 100% (77·0 to 100·0) | 100% (79·3 to 100·0) | 70·1% (−4·9 to 91·5) | 100% (−51·5 to 100·0) | 100% (63·5 to 100·0) | 100% (68·9 to 100·0) | 64·6% (−46·5 to 91·4) | 64·6% (−44·2 to 91·3) |
| p value§ | 0·0012 | 0·0033 | 0·2759 | 0·125 | 0·0471 | 0·0045 | 0·344 | 0·3761 |
Randomly assigned and non-randomly assigned individuals who were allocated to immediate vaccination were combined.
Non-randomised immediate clusters are excluded from this analysis.
From fitting a β-binomial distribution to the cluster-level numerators and denominators and using an inverted likelihood ratio test to identify the lower bound for vaccine efficacy (columns 1, 2, 5, and 6); from a Cox proportional hazards model (column 3, 7, and 8); from signed test (two-sided): probability of observing endpoints in control groups among treatment–control mismatched pairs and under the null hypothesis that the vaccine has no efficacy (column 4).
From Fisher's exact test (two-sided), which is approximate for columns 1 and 2. From signed test (two-sided): probability of observing endpoints in control groups among treatment–control mismatched pairs and under the null hypothesis that the vaccine has no efficacy (column 4).