Preventive effects of influenza and pneumococcal vaccination in the elderly - results from a population-based retrospective cohort study

• Published in: Human vaccines & immunotherapeutics 2021-06, Vol.17 (6), p.1844-1852
• Main Authors: Rose, Norman, Storch, Josephine, Mikolajetz, Anna, Lehmann, Thomas, Reinhart, Konrad, Pletz, Mathias W, Forstner, Christina, Vollmar, Horst Christian, Freytag, Antje, Fleischmann-Struzek, Carolin
• Format: Article
• Language: English
• Subjects: influenza; pneumococci; pneumonia; Research Paper; sepsis; Vaccine effectiveness
• ISSN: 2164-5515; 2164-554X
• DOI: 10.1080/21645515.2020.1845525

Influenza and pneumococcal vaccinations are recommended in the elderly to reduce life-threatening complications like sepsis. Protection may be reduced with increasing age. We aimed to assess the effectiveness of both vaccines in the elderly by performing a retrospective cohort study of 138,877 individuals aged ≥60 y in Germany, who were insured in a large statutory health insurance (AOK PLUS). We used longitudinal claims data to classify individuals according to vaccination status 2008-2014, and assessed vaccine effectiveness (VE) in 2015 and 2016. Inverse probability weighting based on generalized propensity scores was used to adjust for systematic between-group differences. Influenza vaccination was associated with a reduction of hospital treatment in laboratory-confirmed influenza in 2015 (VE = 41.32 [95%CI 0.85, 65.26]), but had no significant impact on the overall influenza incidence. Complications of influenza (pneumonia and sepsis) were reduced in 2016. We found a rise in influenza-like illness and acute respiratory infections in both years and an increased 90-d mortality after hospital-treated pneumonia in vaccinees in 2015. Pneumococcal vaccination was effective in preventing hospital-treated pneumonia within the first and second year after vaccination (VE = 52.45 [13.31, 73.92] and 46.04 [5.46, 69.21], respectively), but had no impact on sepsis incidence or pneumonia mortality. Influenza and pneumococcal vaccination can prevent severe complications from influenza and hospital-treated pneumonia in the elderly, respectively. Vaccine effects differ between years and seasons and are partly difficult to interpret. Despite extensive efforts to adjust for between-group differences, residual bias cannot be ruled out, possibly explaining signals like increased ILI or pneumonia mortality.