EFFECT OF INFLUENZA AND PNEUMOCOCCAL VACCINES IN ELDERLY PERSONS IN YEARS OF LOW INFLUENZA ACTIVITY

This study was undertaken to assess the preventive effect of influenza and pneumococcal vaccination in reducing hospitalisation and length of hospital stay (LOHS) even during periods of low influenza activity. This was a prospective study conducted from 2003-2005, among individuals above 65 years in a region close to the Stockholm urban area. The specificity of the apparent vaccine associations were evaluated in relation to the influenza seasons. The total study population in 2003 was 41,059, of which 31% received influenza vaccine of these and of them 11% were administered the pneumococcal vaccine. In 2004, 34% individuals received the influenza vaccine and 21% received the pneumococcal vaccine and in 2005 39% individuals were given the influenza vaccine and 28% received the pneumococcal vaccine. The findings indicate that 35% of the vaccinated belonged to a medical risk category.. Data on hospitalisation and mortality during the 3-year period were obtained and, during the influenza seasons, reduction of hospital admissions and significantly shorter in-hospital stay for influenza was observed in the vaccinated cohort (below 80 years of age). For individuals who also had received the pneumococcal vaccine, a significant reduction of hospital admissions and of in-hospital stay was observed for invasive pneumococcal disease and for pneumococcal pneumonia. Effectiveness was observed for cardiac failure even in persons that also had received the pneumococcal vaccine, despite that the pneumococcal vaccinated mainly belonged to a medical risk category. Reduction of death from all causes was observed during the influenza season of 2004, in the 75-84-year old age group and in all age-groups during the influenza season 2005. This study confirmed the additive effect of the two vaccines in the elderly, which was associated with a reduced risk in hospitalisation and a reduction in mean LOHS in seasons even with a low influenza activity.