| Study characteristics |
| Methods |
Retrospective cohort study conducted in 46 elderly homes in Hong Kong, China to assess the effectiveness of influenza vaccination on influenza, pneumonia, hospitalisation for influenza, and death. People were eligible if they were age 65 years or above. The exposed group comprised people who had not received influenza vaccination, while the control group comprised people who had received influenza vaccination from the Department of Health or other healthcare providers in 2004. Information regarding vaccination was based on its documentation in the elderly home records. A resident having unknown history of influenza vaccination in the preceding calendar year was regarded as not being vaccinated. A standardised questionnaire was used to collect data from the elderly homes once an influenza outbreak was defined in the elderly home. The occurrence of influenza was identified by the self administered questionnaires. The occurrence of pneumonia, hospitalisation, and death were identified from the hospital records. |
| Participants |
3177 residents participated in the study. The mean age was 83 years; 2133 were females and 1044 males. There were 2943 vaccinated (92.6%) and 234 (7.4%) unvaccinated participants. More females were vaccinated (67.7%) than males (59.8%). |
| Interventions |
Influenza vaccination versus no vaccination |
| Outcomes |
Influenza, pneumonia, hospitalisation, and death |
| Notes |
The authors conclude that this study failed to demonstrate a protective effect of influenza vaccine against influenza and its complications during outbreaks. |
