Seasonal influenza and pneumococcal vaccination in institutionalized older adults

Influenza (IV) and pneumococcal polysaccharide vaccination (PPV) may reduce hospitalization and mortality but the effectiveness of these vaccines in older adults (≥65 years) is controversial. This thesis includes seven parts with a total of ten studies studying different aspects regarding IV and PPV in institutionalized older adults - the group with the highest infection-related morbidity and mortality. In Part I, we presented the controversies about effectiveness of influenza and pneumococcal vaccination in institutionalized older adults. In Part II, we studied a retrospective cohort of 1737 older adults showing that nursing home residence is independent risk factor of infection-related mortality and hospitalization. In Part III, the second and third studies were systematic reviews showing that IV and PPV could reduce pneumonia and death.. In Part IV, we evaluated the effectivenss of IV and PPV through prospective cohorts. The fourth study was a prospective cohort study of 1859 institutionalized older adults showing that IV significantly reduced mortality and hospitalization. The fifth study was a prospective cohort study of 532 institutionalized older adults showing that when the IV strain does not match the circulating strain, PPV provided additional protection in reducing mortality. In Part V, the sixth study was a randomized controlled trial of 100 institutionalized older adults showing that intradermal IV has better immunogenicity than intramuscular vaccination without compromising safety. In Part VI, we identified factors that may affect clinical effectiveness of IV. The seventh and eighth studies were prospective cohort studies of 711 institutionalized older adults showing that vaccine efficacy declined with increasing impaired functional status and renal function. In Part VII, we identified determinants of receiving IV and PPV in institutionalized older adults. The ninth study was a cross-sectional study of 155 institutionalized older adults showing that encouragement from nHCWs was a major facilitator of receiving vaccination. The tenth study was a cross-sectional study of 1300 nHCWs showing that 40.2% of nHCWs had encouraged residents to receive vaccination. In conclusion, ten studies from this thesis demonstrated that IV and PPV are effective in preventing hospitalization and reducing mortality in institutionalized older adults. Different strategies in improving its effectivenss and acceptance were suggested.published_or_final_versionMedicineMasterDoctor of Medicin