Near-Real Time Assessment of 2009-10 Seasonal and Pandemic Influenza Vaccine Coverage, Using Private Sector Surveillance Systems

Background: SDI tracks influenza by collecting clinical, demographic, vaccine status, medical history and rapid testing data from ~20,000 patients with influenza-like illness (ILI) seen in ~400 primary physician offices across the US each season.  Furthermore, SDI tracks patterns in vaccine dose administration in physician's offices using a large national sample of medical claims.

Objectives: To generate near-real time influenza vaccine coverage estimates

Methods: We estimated influenza vaccination coverage from the primary surveillance system in the subset of ILI patients seen during November 1 through December 10 2009, and who tested negative for influenza virus.  Medical claims data from CMS-1500 forms featuring procedure codes for pandemic and seasonal doses were used to generate temporal uptake patterns and total doses administered in physician's offices. 

Results: We included 1607 rapid-test negative ILI patients in the study; of these, 431 had received seasonal vaccine, 111 the pandemic vaccine and 84 had both.  For persons aged <5, 5-18, 19-64, and 65+ years the coverage was 41%, 25%, 21%, 49% for seasonal- and 13%, 8%, 4%, 6% for pandemic vaccine.  For persons with high-risk conditions, the figures were 65%,36%,31%,66% for seasonal and 21%,11%,5%, 8% for pandemic vaccine.  Claims data showed that seasonal vaccine uptake peaked early October and the cumulative national private sector administrations leveled off at ~30M doses, compared to 30-37M doses in prior 3 seasons (for seniors, 8M compared to 10-12M doses).  Pandemic dose uptake was still increasing in early December, at which point ~7M doses had been administered.

Conclusions: Across two SDI surveillance systems, we generated near-real time estimates of seasonal and pandemic vaccine coverage and uptake patterns for 2009-10.  Despite early availability, senior vaccine coverage (49%) was far lower than that in prior years.  Pandemic vaccine coverage was low in all age groups, reflecting late availability and restriction to high risk groups, and will likely increase over time.