Methods: Sixty-four studies with adults older than 65 years old were included in the assessment of the effects of vaccinations of the elderly. Data were analyzed after studies were categorized according to the setting of the study (i.e., long-term care facilities and the community), level of viral circulation and the vaccine-virus match. Analyses were conducted to eliminate the influence of external variables (e.g., age). The effects of the influenza vaccination were described by the ability to reduce cases of influenza, influenza-like-illnesses (e.g., coughing), influenza-related hospitalization and death.

More specifically, seven of the 64 selected studies were reviewed as they included information from which safety of the influenza vaccinations could be assessed. In this study safety was calculated by the absence of local and systematic side- effects after the vaccinations.

Findings: In long-term care facilities, vaccines that match with the viral strains of influenza (i.e., wellmatched vaccines) were found to be the most effective during influenza outbreaks. Well matched vaccines had a preventive effect against 42% of deaths due to influenza or pneumonia. Its effectiveness in preventing influenza- or pneumonia-related hospitalization was 45% during outbreaks, and 68% during periods of low viral circulation. Its effect in preventing pneumonia was 46%.

Among community-dwelling elderly, well-matched vaccines were effective at preventing hospitalization due to influenza or pneumonia. After the influence of external factors (e.g., age) were eliminated, vaccinations were found to be effective at preventing 22% of respiratory diseases, 24% of cardiac diseases, and 26% of influenza- or pneumonia-related hospitalizations. Vaccination against influenza was not found to be as effective among community-dwelling elderly. The authors concluded that the uptake of vaccines is linked to factors such as socio-economical status and health conditions, which in turn influences the measurement of the effects of vaccines.

Among all the reviewed studies, no side-effects (e.g., fever and depression) were found to be associated with the influenza vaccine. The authors concluded that the vaccines are safe to be used.

Conclusions: In general, the influenza vaccines appear to be safe as no local and systemic side effects were identified. Particularly, vaccines that match the influenza viral strains are most effective at preventing influenza complications in long-term care facilities. To further reduce viral transmission, vaccinating the service providers in the long-term care facilities is also suggested.

Reference: Rivetti, D., Jefferson, T., Thomas, R., Rudin, M., Rivetti, A., Di, Pietrantonj, C., Demicheli, V. "Vaccines for preventing influenza in elderly." Cochrane Database of Systematic Reviews 2006, Issue 3.

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