Table 2.
Vaccination effects in healthcare workers (the occupational health perspective)
| Review ID | Population | Laboratory-confirmed influenza |
Clinically suspected influenza |
SR authors’ conclusions |
|||
|---|---|---|---|---|---|---|---|
| No. of studies (participants) | Efficacy (95% CI) | No. of studies (participants) | Efficacy (95% CI) | On efficacy | For policy | ||
| Ng and Lai12 | HCW | 1 RCT (359) | 88% (59 to 96) | 2 RCTs (606) | No significant effect in either study | ‘No definitive conclusion on the effectiveness of influenza vaccinations in HCWs’ | ‘Further research is necessary to evaluate whether annual vaccination is a key measure to protect HCWs’ |
| Burls et al13 | HCW | 1 RCT (361) | 88% (47 to 97) Inf. A 89% (14 to 99) Inf. B |
2 RCTs (606) | No significant effect in either study | ‘Vaccination was highly effective’ | ‘Effective implementation should be a priority’* |
| Michiels et al14 | HCW | 1 non-RCT (262) | 90% (25 to 99) | 1 RCT (346) | 53% (NS) p=0.002 | None stated | None stated |
| Demicheli et al19 | Healthy adults | 22 RCTs (51 724) | 62% (56 to 67) | 16 (25 795) | 17% (13 to 22) | ‘Influenza vaccines have a very modest effect in reducing influenza symptoms’ | ‘Results seem to discourage the usage of vaccination against influenza in healthy adults as a routine public health measure.’† |
| DiazGranados et al15 | Healthy adults | Not stated | 59% (50 to 66) | – | – | ‘Influenza vaccines are efficacious’ | None stated |
| Osterholm et al17 | Healthy adults | 6 (31 892) | 59% (51 to 67) | – | – | ‘Influenza vaccines provide moderate protection against confirmed influenza’ | None stated |
| Villari et al18 | Healthy adults | 25 (18 920) | 63% (53 to 71) | 49 (46 022) | 22% (16 to 28) | ‘Estimates (of effect) vary substantially’ | ‘Further trials…are needed to provide definitive answers for policymakers’ |
| Michiels et al14 | Healthy adults | 14 (21 616) | 44% to 73% (range) | 19 (19 046) | No significant effect | ‘Inactivated influenza vaccine shows efficacy in healthy adults’ | None stated |
| Ferroni and Jefferson16 | Healthy adults | 5 (43 830) | 44% to 77% (range) | 18 (19 046) | 7% to 30% (range) | ‘Inactivated vaccines are effective at reducing infection’ | None stated |
*This conclusion may be influenced by the reported effects on protecting patients and days off work in tables 3 and 4, respectively.13
†This conclusion is influenced by the additional findings of no demonstrable effect on complications such as pneumonia or transmission.19
HCW, healthcare worker; RCTs, randomised controlled trials; SR, systematic review.