1. Studies included in the various versions of this review and their impact on our conclusions.
| Review version (searches date) | Number of included trials (RCTs/CCTs) | Number of included observational studies | Estimates of effect (RCTs/CCTs only) | Conclusions (1 to 2 lines from abstract) |
| Version 1 (24 May 2006) |
9 | 621 |
Influenza‐like illness LAIV = no data TIV = 41% (95% CI 27% to 53%) IAV = n.s. Influenza LAIV = n.s. TIV = 58% (95% CI 34% to 73%) IAV = n.s. |
In long‐term care facilities, where vaccination is most effective against complications, the aims of the vaccination campaign are fulfilled, at least in part. However, according to reliable evidence the usefulness of vaccines in the community is modest. The apparent high effectiveness of the vaccines in preventing death from all causes may reflect a baseline imbalance in health status and other systematic differences in the 2 groups of participants. |
| Version 2 (20 January 2010) |
9 | 662 |
Influenza‐like illness LAIV = no data TIV = 41% (95% CI 27% to 53%) IAV = n.s. Influenza LAIV = n.s. TIV = 58% (95% CI 34% to 73%) IAV = n.s. |
The available evidence is of poor quality and provides no guidance regarding the safety, efficacy, or effectiveness of influenza vaccines for people aged 65 years or older. To resolve the uncertainty, an adequately powered publicly‐funded randomised, placebo‐controlled trial run over several seasons should be undertaken. |
1These include 49 cohort studies for efficacy/effectiveness (79 data sets); 10 case‐control studies for efficacy/effectiveness (12 data sets); 3 studies (cohorts) for Guillain‐Barré syndrome. 2For this update, two cohort studies and two case‐control studies were added to the review (all assessing efficacy/effectiveness).
Key: CCT = controlled clinical trial; CI = confidence interval; IAV = inactivated aerosol vaccines; LAIV = live attenuated vaccines; n.s. = not significant; RCT = randomised controlled trial; TIV = trivalent inactivated vaccines