Abstract
BackgroundInfluenza pandemic outbreaks occurred in the US in 1918, 1957, and 1968. Historical evidence suggests that the majority of influenza-related deaths during the 1918 US pandemic were attributable to bacterial pneumococcal infections. The 2009 novel influenza A (H1N1) outbreak highlights the importance of interventions that may mitigate the impact of a pandemic.MethodsA decision-analytic model was constructed to evaluate the impact of 7-valent pneumococcal conjugate vaccine (PCV7) on pneumococcal disease incidence and mortality during a typical influenza season (13/100) and a severe influenza pandemic (30/100). Outcomes were compared for current PCV7 vaccination practices vs. no vaccination. The model was estimated using published sources and includes indirect (herd) protection of non-vaccinated persons.ResultsThe model predicts that PCV7 vaccination in the US is cost saving for a normal influenza season, reducing pneumococcal-related costs by $1.6 billion. In a severe influenza pandemic, vaccination would save $7.3 billion in costs and prevent 512,000 cases of IPD, 719,000 cases of pneumonia, 62,000 IPD deaths, and 47,000 pneumonia deaths; 84% of deaths are prevented due to indirect (herd) protection in the unvaccinated.ConclusionsPCV7 vaccination is highly effective and cost saving in both normal and severe pandemic influenza seasons. Current infant vaccination practices may prevent >1 million pneumococcal-related deaths in a severe influenza pandemic, primarily due to herd protection.
Highlights
Influenza pandemic outbreaks occurred in the US in 1918, 1957, and 1968
Consistent with other economic models [21,22] and the Northern California Kaiser Permanente (NCKP) trial [23], meningitis and bacteremia are defined as those caused by S. pneumoniae, whereas pneumonia and acute otitis media (AOM) cases are caused by any organism
Non-pandemic influenza season The model predicts that current vaccination practices prevent approximately 32,300 invasive pneumococcal disease (IPD) cases, 550,100 pneumonia cases, 2,200 IPD deaths, and 21,000 pneumonia deaths during a normal influenza season
Summary
Influenza pandemic outbreaks occurred in the US in 1918, 1957, and 1968. Historical evidence suggests that the majority of influenza-related deaths during the 1918 US pandemic were attributable to bacterial pneumococcal infections. More recent studies support the conclusions of investigators at the time of the pandemic [7] that most deaths were due to complications of bacterial pneumonia. A study of autopsy samples from victims of the 1918 pandemic found bacteria in all samples, pointing to bacterial pneumonia as the cause of death [8]. A recent autopsy study of H1N1 victims found bacterial pneumonia in 55% of their samples [10]. These observations are further supported by a recent double-blind randomized trial of pneumococcal conjugate vaccine in children not vaccinated for influenza that demonstrated a 45% lower incidence of hospitalization due to influenza-associated pneumonia among those receiving the pneumococcal vaccine [11]
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