Puig‐Barbera 2007.

Study characteristics
Methods	3 case‐control studies were performed in the elderly population (> 64 years of age) of 3 health districts in the Valencia Autonomous Region, Spain (total number of elderly residents in these districts: n = 105,454 at 31 December 2004), where MF59‐adjuvanted subunit influenza vaccine was used. The risk of hospitalisation for ACS, CVA, or pneumonia was evaluated for people who had received influenza vaccine and for those who had not received influenza vaccine.
Participants	Description of cases Incident cases for each disease were identified from all consecutive emergency hospitalisations following their admission between 15 November 2004 and 31 March 2005. Diagnoses were made according to the International Classification of Diseases, 9th version, Clinical Modification for ACS (410‐411.89 and 413), CVA (431‐436), or pneumonia (480‐487). Only non‐institutionalised patients who were > 64 years of age, had lived in the hospital catchment area for the previous 6 months, were able to give informed consent, and remained in hospital for at least 72 hours were included in the study. After consideration of the exclusion criteria, 144 cases admitted for ACS, 134 for CVA, and 198 for pneumonia were included in the study. Description of controls Each case was paired with 1 or 2 controls, matched for hospital and gender. Controls were recruited based on the same inclusion criteria as cases, following emergency hospitalisations for an acute surgical process or trauma. The admission date for controls was matched to the case admission date, preferably being the same day, and with a maximum interval of 10 days. 258 controls were admitted for ACS, 246 for CVA, and 321 for pneumonia. A total of 75.2% and 78.1% of vaccinated cases and controls, respectively (P = 0.314) were vaccinated and on the population register. Of these, all cases and 99.73% of controls had received MF59‐adjuvanted subunit influenza vaccine.
Interventions	Influenza vaccination and hospitalisation for ACS, CVA, and pneumonia
Outcomes	—
Notes	The authors conclude that the results suggest that MF59‐adjuvanted influenza vaccination is associated with a significant reduction in the risk of hospitalisation for ACS, CVA, and pneumonia during the period of influenza virus circulation.