Despite well-documented evidence regarding effectiveness and safety, uptake of influenza vaccine among adults in the United States falls short of targeted rates.1,2 Efforts to increase influenza vaccine uptake have focused on reducing the number of so-called missed opportunities, ie, patients who visit health care providers during the fall without being vaccinated.1,3 Yet, the potential effectiveness of provider-based strategies for reducing missed opportunities (eg, standing orders, computerized reminders) may be overstated without consideration of patients' willingness to be vaccinated. We present a more realistic estimate of the potential of such strategies to increase influenza vaccine uptake by quantifying the number of unvaccinated adults most amenable to vaccination during a fall visit to a health care provider.
We analyzed data from a nationally representative survey of US adults 18 years and older (N = 5067) fielded by Knowledge Networks, Menlo Park, California, between March 4 and April 7, 2009. Knowledge Networks operates an online panel of households that covers both the online and offline populations.4 Sixty-nine percent of sampled panelists responded to the survey. Self-reported influenza vaccination rates derived from the Knowledge Networks panel compare well with those derived from the National Health Interview Survey.5
The survey asked respondents about receipt of influenza vaccine, visits to health care providers during the period from October through December 2008, and willingness to be vaccinated based on a “strong recommendation” from a health care provider. We assessed indications for influenza vaccine based on self-reported age and high-risk health conditions.1 Missed opportunities are calculated as the number of unvaccinated patients with at least 1 health care provider visit between October and December 2008, with or without accounting for patients' willingness to be vaccinated. Uptake and missed opportunity rates were weighted to be nationally representative using the Current Population Survey.6 Estimated numbers of vaccinated and unvaccinated adults were obtained by scaling up estimated vaccination and missed opportunity rates as well as disease prevalence based on the size of the total adult population as of November 1, 2008.7 All calculations were performed using STATA SE version 10.1 software (StataCorp, College Station, Texas).
The Table presents estimates of influenza vaccine uptake, missed opportunities derived from vaccination and fall visit data alone, and an adjusted measure of missed opportunities that is limited to the subgroup of unvaccinated adults who were amenable to being vaccinated based on a health care provider's recommendation. Calculating missed opportunities based on vaccination and care use data alone reveals that there are more than 53 million US adults who had at least 1 health care provider contact between October and December 2008 and nonetheless remained unvaccinated. Vaccinating all of these patients would increase overall vaccination uptake by 23.1 percentage points and result in an overall uptake rate of approximately 62%. Eliminating missed opportunities among those with specific vaccine indications would increase uptake by 19.7 percentage points (diabetes) to 27.4 percentage points (asthma).
Eliminating missed opportunities only among those willing to be vaccinated would result in a 14.4–percentage point increase in vaccine uptake among the general adult population, leading to an overall vaccination rate of approximately 53%. Corresponding subpopulation increases in immunization rates range from 9.6 (diabetes) to 17.5 (asthma) percentage points.
We showed that reducing missed opportunities among the subgroup of adults amenable to health care provider recommendation could yield substantially higher influenza vaccine uptake rates. Our results also suggest that there is a sizable subgroup of patients who see health care providers during the vaccination season, but may be unwilling to get vaccinated in the absence of outreach efforts aimed at overcoming their resistance. Thus, strategies aimed at fully eliminating missed vaccination opportunities need to consider the preferences and beliefs of this group.
Correspondence: Dr Maurer, RAND Corporation, 1200 S Hayes St, Arlington, VA 22202 (firstname.lastname@example.org).
Author Contributions: All authors had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Maurer, Harris, and Lurie. Acquisition of data: Maurer, Harris, and Lurie. Analysis and interpretation of data: Maurer, Harris, and Lurie. Drafting of the manuscript: Maurer, Harris, and Lurie. Critical revision of the manuscript for important intellectual content: Maurer, Harris, and Lurie. Statistical analysis: Maurer, Harris, and Lurie. Obtained funding: Harris and Lurie. Study supervision: Lurie.
Financial Disclosure: None reported.
Funding/Support: This study was supported by GlaxoSmithKline.
Role of the Sponsor: The sponsor had no role in the research design or in the preparation, review, or approval of the manuscript.
Disclaimer: The study design, data management, analysis, and opinions expressed herein are solely those of the authors and do not represent those of RAND or GlaxoSmithKline.
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