Published Online: January 21, 2013
Chyongchiou Jeng Lin, PhD; Richard K. Zimmerman, MD, MPH; and Kenneth J. Smith, MD, MPH
Objectives: Despite the benefits of vaccination and guidelines for their use, the rates for influenza and pneumococcal vaccination remain below the 90% goal set by Healthy People 2010 for persons 65 years and older. Standing order programs (SOPs) authorize vaccination administration without physician orders. Here we examine the cost-effectiveness of SOPs to improve both pneumococcal and influenza vaccination rates in outpatient settings for individuals 65 years and older.
Study Design: Decision analysis-based cost-effectiveness analysis.
Methods: A Markov model was constructed to estimate the incremental cost-effectiveness of outpatient SOPs for pneumococcal polysaccharide vaccine (PPSV) and influenza vaccination in hypothetical US population cohorts 65 years and older. Vaccination rate improvement data were obtained from the medical literature. Centers for Disease Control and Prevention Active Bacterial Core surveillance data and US national databases were used to estimate costs and outcomes.
Results: SOPs cost $14,171 per quality-adjusted life-year (QALY) gained compared with no program from a third-party payer perspective. In 1-way sensitivity analyses, the SOP strategy cost less than $50,000/QALY if SOPs increased absolute vaccination rates by 4% or more (base case: 18%), annual SOP costs were less than $21 per person (base case: $4.60), or annual influenza incidence was 4% or more (base case: 10%). Model results were insensitive to other individual parameter variations, and were supported by a probabilistic sensitivity analysis.
Conclusions: SOPs used to improve PPSV and influenza vaccination rates in outpatient settings is a promising and economically favorable investment, with cost-effectiveness analysis results remaining robust to parameter variation over clinically plausible ranges.
(Am J Manag Care. 2013;19(1):e30-e37)
We examined the cost-effectiveness of using standing order programs (SOPs), which allow influenza and pneumococcal vaccination without a physician order, to improve the suboptimal vaccination rates in older US populations.
Administering pneumococcal and influenza vaccines in outpatient settings under SOPs was economically favorable and can impact public health through higher vaccination rates.
Results were robust to parameter variation over clinically plausible ranges.
In a time of healthcare reform and physician shortages, our results support wider use of SOPs.
Pneumonia and influenza continue to be among the leading causes of death in the United States.1 Influenza is estimated to cause an average of 200,000 hospitalizations and 36,000 deaths annually.2 Because individuals 65 years and older are at increased risk for influenza complications, seasonal influenza vaccination is important. Invasive pneumococcal disease (IPD), which includes bacteremia and/or infection of the meninges, joints, bones, or body cavities, is a relatively common outcome following influenza, particularly among individuals with chronic illnesses.3,4 Each year pneumococcus causes about 500,000 cases of pneumonia, 50,000 cases of bacteremia, 3000 cases of meningitis, and up to 7000 to 12,500 deaths.5
The Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) has recommended influenza vaccination for all persons 6 months and older; pneumococcal polysaccharide vaccine (PPSV) is recommended for all persons 65 years and older, and for persons with chronic medical conditions 18 years and older.6 Among persons 65 years and older in 2010, the annual seasonal influenza vaccination rate was 63.6%,7 while 59.4% reported ever receiving PPSV.8 Despite the benefits of adult vaccination and the availability of usage guidelines, vaccination rates for seasonal influenza and PPSV remain below the Healthy People 2020 goal of 90% for each vaccine among persons 65 years and older.9
Standing orders authorize nurses and pharmacists to administer vaccinations according to a protocol approved by an institution or physician without an individual order or examination by the physician.10 The Task Force on Community Preventive Services reviewed the evidence for standing orders and strongly recommended them.11,12 Several studies have reported the successful use of standing order programs (SOPs).13-15 Because both PPSV and influenza vaccination are recommended for persons 65 years and older, coadministration is another strategy to raise vaccination rates. Although Smith et al found that dual PPSV and influenza vaccination of all persons 50 years and older was economically reasonable,4 the cost-effectiveness of SOPs for vaccination of PPSV and influenza vaccine administered in outpatient settings for persons 65 years and older is unknown.
A Markov model was constructed to estimate, from the third-party payer and societal perspectives, the incremental cost-effectiveness of an SOP intervention for PPSV and influenza immunization. The intervention is implementation of SOPs in outpatient practice, and the comparison is between a base case of current practice (including some SOP-using practices) and broader SOP implementation in primary care practices for hypothetical cohorts of patients 65 years and older in the United States.
Figure 1 presents a state transition diagram illustrating the Markov model, which was adapted from a prior study.4 During each monthly cycle, a person may stay well, develop nonsevere influenza, develop severe influenza, or develop IPD without influenza. Severe influenza was defined as requiring inpatient treatment while non-severe influenza was defined as those cases not requiring inpatient therapy. Inpatients with severe influenza may develop IPD, become disabled, or die due to influenza or other causes. We assumed that patients with non-severe influenza would recover and not go on to worse outcomes, depicted by arrows from the illness states to the well state. In the model, influenza occurs in 5-month seasons each year, with annual influenza vaccination at the start of each season, equal monthly incidence within that time frame, and constant yearly incidence over time. PPSV was given, based on the likelihood of vaccination, when patients entered the model; we assumed that no PPSV was given later in the model and no repeat PPSV vaccination. Patients who develop IPD may recover without disability, become disabled, or die. The cohort was followed monthly over their lifetimes until death. Age-specific mortality not associated with illness was based on US mortality tables.16
Generally, US national databases and published sources were used to estimate costs and outcomes, which were discounted at an annual rate of 3%.17,18 PPSV effectiveness was estimated based on an expert panel, consisting of present and former CDC ACIP members or liaisons and other pneumococcal disease experts (Table 1), as described previously.19 Because PPSV is generally thought to have little or no effectiveness against non-bacteremic pneumonia,20,21 we conservatively assumed no PPSV effectiveness against pneumonia. IPD data were obtained from the CDC’s active bacterial core (ABC) surveillance data (Table 2).22 Costs were derived from the medical literature, Medicare physician fees,23 and the 2006 nationwide inpatient sample (NIS) data. Hospitalization charges from NIS data were adjusted using costto- charge ratios from the Medicare cost report.24 Parameter values used in the model are summarized in Table 3.4,15,25-36 In addition, the following assumptions were included in the model: (1) equal likelihood and severity of side effects for each vaccine, (2) patients with immunocompromising conditions gain no benefit from PPSV,4,19,37 (3) 60.1% vaccine uptake for both vaccines, based on National Health Interview Survey (NHIS) data,38 (4) yearly SOP costs remain constant through the lifetime of the modeled patient cohort, and 5) vaccination rates remain constant at the improved rate resulting from SOP use.
The numerator of the cost-effectiveness ratio represents per patient change in resources associated with the SOP including vaccine and administration costs, disease costs, and SOP costs. Details about the estimation of those costs are published elsewhere.4,15,21,24,35,36 SOP costs are derived from time and motion studies of an inpatient program,15 and thus may over- or under-estimate the costs of outpatient programs; for this reason, these costs were varied widely in sensitivity analyses. SOP costs in the model are per person in contact with the implemented program, not per person vaccinated. The denominator of cost-effectiveness ratio represents differences in quality-adjusted life-years (QALYs) resulting from increased vaccination rates due to SOP use. QALYs account for changes in both duration and quality of life, and are the product of time spent in a healthy state and the quality of life utility value for that healthy state summed over all healthy states and over time.
In addition to the base case cost-effectiveness analysis, 1-way sensitivity analyses and Monte Carlo probabilistic sensitivity analyses were performed to examine the robustness of cost-effectiveness estimates. One-way sensitivity analyses were conducted for all model parameters in Table 1, varying them over their listed ranges to evaluate influence on model results. In these analyses, the parameter of interest was varied while all other variables remained unchanged from their base case values. The probabilistic sensitivity analysis varied all input parameters simultaneously across their ranges; 10,000 model iterations were performed over specific distributions selected based on the level of parameter value certainty. Tree- Age Pro 2009 (TreeAge Software, Williamstown, Massachusetts) was used to perform the analysis.
From a third-party payer perspective, SOPs cost $14,171 per QALY gained compared with no SOP when the SOPrelated absolute increase in vaccination rate was at its base case level, 18% (Table 4, top). When the societal perspective is taken, which adds costs that patients incur while seeking or receiving care,18 SOPs cost $12,718 per QALY gained. We report all subsequent results from the third-party payer perspective.
In 1-way sensitivity analyses, individual variation of the vaccination rate increase due to SOPs (Table 4) showed that the incremental cost-effectiveness ratio remained less than $50,000 per QALY gained if absolute vaccination rates increased more than or equal to 4%. The effects of varying other selected parameter values in 1-way sensitivity analyses are shown in Figure 2. Of these, program costs and annual influenza probability had the greatest effects on results; however, SOPs cost less than $50,000/QALY if program costs were not greater than $21 per person per year (base case = $4.6015) or annual influenza incidence was more than or equal to 4% (base case = 10%). Varying PPSV effectiveness had little impact on model results, given the relatively low incidence of invasive pneumococcal disease when compared with influenza incidence. With PPSV effectiveness at its low range estimate (Table 1), SOPs cost $14,694/QALY gained, $523 more than the base case value; if PPSV was completely ineffective, SOPs cost $15,577/QALY. Individual variation of the other listed parameters had little effect on model results.
In the probabilistic sensitivity analysis, which varied all parameter values simultaneously over distributions, SOPs were favored in greater than 82% of model iterations if the willingness-to-pay acceptability threshold was $50,000/QALY or more. In this analysis, SOPs were cost saving in 9.6% of iterations and were more costly and less effective than no program in 0.7% of the model iterations.
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