Summary of findings 2. Inactivated influenza vaccine compared to placebo or do nothing for preventing influenza in children.
| Inactivated influenza vaccine compared to placebo or do nothing for preventing influenza in children | ||||||
| Patient or population: healthy, community‐dwelling children older than 2 years of age Setting: influenza seasons in the USA Intervention: inactivated influenza vaccine Comparison: placebo or do nothing | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Risk with placebo or do nothing | Risk with influenza vaccine | |||||
| Influenza assessed by laboratory confirmation Follow‐up over a single influenza season |
Low | RR 0.36 (0.28 to 0.48) | 1628 (5 RCTs) | ⊕⊕⊕⊕ HIGH1 | ||
| 3 per 10001 | 1 per 1000 (1 to 2) | |||||
| Moderate | ||||||
| 298 per 1000 | 107 per 1000 (83 to 143) | |||||
| High | ||||||
| 481 per 1000 | 173 per 1000 (135 to 231) | |||||
| Influenza‐like illness assessed by subjective report Follow‐up over a single influenza season |
Low | RR 0.72 (0.65 to 0.79) | 19,044 (4 RCTs) | ⊕⊕⊕⊝ MODERATE2 | ||
| 134 per 10001 | 96 per 1000 (87 to 106) | |||||
| Moderate | ||||||
| 282 per 1000 | 203 per 1000 (183 to 223) | |||||
| High | ||||||
| 328 per 1000 | 236 per 1000 (213 to 259) | |||||
| Otitis media assessed by clinical confirmation (inspection of ear and symptoms) Follow‐up over a single influenza season |
271 per 1000 | 312 per 1000 (257 to 379) |
RR 1.15 (0.95 to 1.4) |
884 (3 RCTs) |
⊕⊕⊕⊝ MODERATE3 | |
| Absence from school Follow‐up over a single influenza season |
92 per 1000 | 42 per 1000 (16 to 112) |
RR 0.46 (0.17 to 1.22) |
254 (1 RCT) |
⊕⊝⊝⊝ VERY LOW4 5 | |
| Number of parents having to take off work during follow‐up ‐ not reported | ‐ | ‐ | ‐ | ‐ | ‐ | |
| Hospitalisations ‐ not reported | ‐ | ‐ | ‐ | ‐ | ‐ | |
| Fever ‐ not reported | ‐ | ‐ | ‐ | ‐ | ‐ | |
| Nausea ‐ not reported | ‐ | ‐ | ‐ | ‐ | ‐ | |
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RCT: randomised controlled trial; RR: risk ratio | ||||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect. Moderate quality: We are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low quality: Our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low quality: We have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect. | ||||||
1Control group risks stratified by low, moderate, and high due to wide variation in event rates. 2Downgraded one level due to serious risk of bias. Analysis based on studies at high or unclear risk of bias for multiple domains. 3Downgraded one level due to serious imprecision. Confidence interval includes meaningful increase in otitis media with vaccination. 4Downgraded one level due to serious risk of bias. Study contributing data had multiple domains at unclear risk of bias. 5Downgraded two levels due to very serious imprecision. Low number of events and wide confidence interval.