Abstract
BackgroundInfluenza and pneumonia are leading causes of morbidity and mortality among the elderly. Although vaccination is a main strategy to prevent these infectious diseases, concerns remain with respect to vaccine effectiveness.MethodsDuring three influenza seasons (2014–2015, 2015–2016 and 2016–2017), we evaluated the effectiveness of the influenza and pneumococcal vaccines against pneumonia and acute exacerbation of cardiopulmonary diseases among the elderly aged ≥65 years with influenza-like illness (ILI). Demographic and clinical data were collected prospectively.ResultsAmong 2,119 enrolled cases, 1,302 (61.4%) and 871 (41.1%) received the influenza vaccine and 23-valent pneumococcal polysaccharide vaccine (PPV23), respectively. During an A/H3N2-dominant season with poor influenza vaccine effectiveness (2014–2015 season), neither the influenza vaccine nor PPV23 showed significant effectiveness against pneumonia or acute exacerbation of cardiopulmonary diseases. During seasons with good influenza vaccine effectiveness (2015–2016 and 2016–2017 seasons), the influenza vaccine was effective in preventing pneumonia, but PPV23 was not. In particular, the influenza vaccine was effective in preventing acute exacerbation of heart diseases (75.0%) during the A/H1N1-dominant 2015–2016 season.ConclusionThe influenza vaccine was effective in preventing pneumonia only during vaccine-matched seasons with good effectiveness against circulating influenza viruses. In addition, the influenza vaccine was cardio-protective during a vaccine-matched A/H1N1-dominant season.
Highlights
Influenza disease burden might vary according to regional climate, population density, and seasonal viral antigenic changes, the clinical impact of influenza epidemics has been high worldwide
During three influenza seasons (2014–2015, 2015–2016 and 2016–2017), we evaluated the effectiveness of the influenza and pneumococcal vaccines against pneumonia and acute exacerbation of cardiopulmonary diseases among the elderly aged 65 years with influenza-like illness (ILI)
Influenza-related hospitalizations and deaths are mainly caused by accompanying complications, including pneumonia, acute exacerbation of underlying cardiopulmonary diseases, rhabdomyolysis, and acute renal failure
Summary
Influenza disease burden might vary according to regional climate, population density, and seasonal viral antigenic changes, the clinical impact of influenza epidemics has been high worldwide. In the United States, influenza epidemics are responsible for approximately 20,000 to 40,000 deaths and 114,000 hospitalizations annually [1, 2]. In South Korea, the influenza epidemic during the 2013–2014 season caused an estimated 23,326 hospitalizations and 1,249 deaths [3]. The estimated mean annual influenza-associated excess mortality rate ranges from 0.1–6.4 per 100 000 individuals for people younger than 65 years, 2.9–44.0 per 100 000 individuals for people aged 65–74 years, and 17.9–223.5 per 100 000 for people aged 75 years [4]. Influenza-related hospitalizations and deaths are mainly caused by accompanying complications, including pneumonia, acute exacerbation of underlying cardiopulmonary diseases, rhabdomyolysis, and acute renal failure. Influenza and pneumonia are leading causes of morbidity and mortality among the elderly. Vaccination is a main strategy to prevent these infectious diseases, concerns remain with respect to vaccine effectiveness
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