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Cost-effectiveness of Combined Outreach for the Pneumococcal and Influenza Vaccines
Marcia Weaver, PhD, MA;
James Krieger, MD, MPH;
Joseph Castorina, MD, MPH;
Mary Walls, MPH;
Sandy Ciske, MN
Arch Intern Med. 2001;161:111-120.
ABSTRACT
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Background We conducted a cost-effectiveness analysis as part of a randomized,
controlled trial of a community-based outreach initiative to promote the pneumococcal
and influenza vaccines for people aged 65 years or older.
Methods The analysis was based on primary data from the trial on the increase
in vaccination rates and cost of the intervention, and published estimates
of the effectiveness of the vaccines and cost of treatment. We performed partial
stochastic analyses based on the confidence intervals (CIs) of the effectiveness
of the intervention and of the vaccines.
Results The cost-effectiveness ratio of the combined-outreach initiative as
implemented was $35 486 per quality-adjusted life-year (QALY), whereas
it was $53 547 per QALY for the pneumococcal vaccine and $130 908
per QALY for the influenza vaccine. In partial stochastic analyses, the quasi-CI
of the combined-outreach initiative ranged from $15 145 to $152 311
per QALY. The cost-effectiveness ratio of the intervention targeted to people
who had never received the pneumococcal vaccine or who had not received the
influenza vaccine in the previous year was $11 771 per QALY, with a quasi-CI
of $3330 to $46 095 per QALY. With the use of the projected cost of replicating
the intervention, the cost-effectiveness ratio was $26 512 per QALY for
the initiative as implemented and $7843 per QALY for a targeted initiative.
Conclusions The community-based outreach initiative to promote the pneumococcal
and influenza vaccines was reasonably cost-effective. Further improvements
in cost-effectiveness could be made by targeting the initiative or through
lessons learned during the first year that would reduce the cost of the initiative
in subsequent years.
INTRODUCTION
PNEUMOCOCCAL and influenza infections continue to cause substantial
morbidity and mortality,1, 2, 3, 4, 5
and immunization against these infections remains an important public health
activity. Several major advisory groups recommend the pneumococcal vaccine
(Pneumovax)5, 6, 7
and the influenza vaccine6, 7, 8, 9
for people aged 65 years and older, and research has shown that the vaccines
are cost-effective. The pneumococcal vaccine was cost saving in preventing
pneumococcal bacteremia among people aged 65 years and older.10
The influenza vaccine was cost saving or the net cost per person vaccinated
was about $7# for people aged 65 years and older.11, 12, 13, 14
(A number sign [#] denotes that the estimates were adjusted to 1996 dollars15 to the extent information in the original article
was available to do so.)
Less is known about the cost-effectiveness of interventions to promote
the vaccines, and there has never been a cost-effectiveness analysis (CEA)
of a community-based outreach initiative. Previous researchers analyzed interventions
by providers or insurers to promote the influenza vaccine, including letter
or postcard reminders from physicians' offices,16, 17, 18
telephone reminders from nurses,17 personal
reminders from physicians,17 and letter reminders
from community pharmacists.19 Estimates of
the cost per additional person vaccinated ranged from $5# to $20# for the
intervention to promote the vaccine and from $14# to $32# for the intervention
plus the vaccine.
We conducted a CEA as part of a randomized controlled trial of a community-based
outreach initiative to promote the pneumococcal vaccine and influenza vaccine
for people aged 65 years and older.20 The research
presented below extends the literature on the cost-effectiveness of interventions
to promote vaccines with 3 innovations. (1) It was the first CEA of a community-based
outreach initiative in which effectiveness was measured in quality-adjusted
life-years (QALYs). (See Krieger et al20 for
estimates of the cost per person vaccinated.) (2) It was conducted from a
societal perspective and conformed to the reference case recommended by the
US Panel on Cost-effectiveness in Health and Medicine.21
It was based on primary data from a randomized controlled trial on the increase
in the vaccination rate and the cost of the intervention and published estimates
of the effectiveness of the vaccines in preventing illness and mortality and
costs of treatment. (3) It demonstrated how the methods currently recommended
for CEA can be used to add costs and effectiveness across more than 1 vaccine
in a combined outreach initiative, or more generally across more than 1 CEA
for any combined intervention.
MATERIALS AND METHODS
RANDOMIZED CONTROLLED STUDY OF COMBINED OUTREACH FOR THE PNEUMOCOCCAL
AND INFLUENZA VACCINES
The population, interventions, and outcome measures of the trial are
described briefly below. Pls see Krieger et al20
for a report of the randomized controlled trial that conforms to the recommendations
of Begg and colleagues.22
Study Site and Population
The intervention was conducted at an urban senior center in Seattle,
Wash, from October 14 to November 22, 1996. Participants were recruited from
the senior center membership and a marketing database with seniors who resided
in the 5 contiguous ZIP codes. Potential participants were mailed an invitation
letter and a baseline questionnaire. Those who returned the survey and met
the study inclusion criteria (aged 65 years or older and residence in the
targeted ZIP code areas) were enrolled. No exclusion criteria were applied.
As shown in Figure 1, 1246 people
were enrolled and randomized at baseline and 1083 people completed the follow-up
survey. Randomization was by systematic allocation of alternate respondents
to either control or intervention groups.
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Figure 1. Study participants for the randomized
controlled study of combined outreach for the pneumococcal and influenza vaccines.
Reprinted by permission of Elsevier Science from Krieger et al.20
Copyright 2000 by American Journal of Preventive Medicine.
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Intervention
For the intervention group, a project coordinator sent each participant
a specially designed educational brochure and a postage-paid reply card for
tracking immunization status. If the participant replied that he or she had
not been vaccinated or if the card was not returned, a senior volunteer called
the participant. Senior volunteers received training about the pneumococcal
and influenza vaccines and were responsible for contacting 20 to 25 participants.
The volunteers received technical support from the project coordinator.
Other vaccine promotion activities at the senior center were available
to both the intervention and control groups, including a volunteer nurse who
was on site for 2 hours each weekday to give vaccines free of charge, and
announcements about vaccines appeared in the newsletter and were announced
at events. Vaccines were also given at other community sites, such as pharmacies
and grocery stores, and the regional Medicare provider review organization
sent letters to all African Americans in King County (in which Seattle is
located) who were enrolled in Medicare in October 1995 and October 1996 to
encourage them to get the influenza vaccine.
Outcome Measures
The primary outcomes were the proportion of individuals who reported
receiving the pneumococcal vaccine and the proportion who reported receiving
the influenza vaccine. Use of self-report data on immunization status is a
common practice.23 Data were collected through
the baseline survey in September 1996 and the follow-up survey in March 1997.
MODEL FOR THE CEA
The CEA of the combined-outreach initiative was constructed from 2 independent
analyses: (1) the pneumococcal vaccine against pneumococcal bacteremia and
(2) the influenza vaccine against influenza and pneumonia. Figure 2 is a model that shows these 2 relationships, as well as
a possible relationship between the pneumococcal vaccine and pneumococcal
pneumonia. The analysis does not include the pneumococcal vaccine against
pneumococcal pneumonia, because the vaccine's effectiveness among people aged
65 years and older is controversial. The results of a recent clinical trial
showed that the vaccine was not effective among the elderly who had previously
been treated as inpatients for community-acquired pneumonia.24
In addition, a recent meta-analysis of randomized controlled trials showed
that the vaccine was not effective in reducing the incidence of definitive
pneumococcal pneumonia or mortality among high-risk patients, which included
the elderly.25 (See the "Comment" section.)
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Figure 2. Model showing the relationship
between the vaccines and the illnesses and outcomes they were intended to
prevent.
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There is a decision tree for each independent CEA. A sample decision
tree for the influenza vaccine is displayed in Figure 3. The decision tree begins on the left side and shows the
initial randomization of participants into either the intervention or control
group. Moving to the right, participants made a decision about getting a vaccine,
but the probability of getting a vaccine was higher for the intervention group
than the control group. Next, some participants became ill and others did
not, but the probability of becoming ill was lower for people who were vaccinated
than for those who were not. Finally, some participants died and other did
not, but the probability of dying was lower for people who were vaccinated
than for those who were not, because the vaccine eliminated influenza and
pneumonia as a cause of death when it was effective. The last branch of the
tree embodies the assumption that the vaccine affected the incidence of the
illnesses, but not the severity when they occurred. The last branch also reflects
the competing risk analysis in which the vaccine affected mortality from influenza
and pneumonia, but not from other causes.26
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Figure 3. Decision tree for an intervention
to promote only the influenza vaccine.
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The decision tree for bacteremia (not shown) would be similar to Figure 3, but it would have 6 cycles rather
than 1 cycle, because the duration of immunity for the pneumococcal vaccine
was 6 years and the duration for the influenza vaccine was 1 year.
For each independent CEA, we performed 5 different calculations. First,
we performed 2 calculations for each group: (1) the total cost of the intervention
(when relevant), vaccine (including treatment of side effects), and treatment
of illnesses, and (2) the total QALYs lost because of vaccine side effects,
morbidity, and mortality. Then, between the intervention and control groups,
we calculated the marginal cost and marginal effectiveness, which were the
difference between the costs and the QALYs, respectively, of the groups. Finally,
we calculated the cost-effectiveness ratio, which was the ratio of marginal
cost to marginal effectiveness.
For the CEA of the combined outreach initiative, we performed the same
5 calculations with the use of the sum of the costs and effectiveness of each
independent analysis. The cost of the intervention, however, was counted only
once. In addition, when people got the influenza and pneumococcal vaccines
at the same time, the participants' expenditures for transportation and the
social cost of the participants' and caregivers' time to obtain the vaccines
were counted only once. The CEA of the combined outreach initiative did not
allow for an interaction between the effectiveness of the pneumococcal vaccine
and the influenza vaccine. Previous research suggested that there was no incremental
effect of the pneumococcal vaccine in preventing pneumonia or pneumococcal
pneumonia among elderly people who received the influenza vaccine,27 but neither was there a reduction in effectiveness.28
UNCERTAINTY
The major sources of uncertainty that were incorporated into the model
were the effectiveness of the intervention and the effectiveness of the vaccines.
To address this uncertainty, we performed partial stochastic CEAs.29 For these analyses, we calculated quasi–confidence
intervals (CIs) for the cost-effectiveness ratio based on the CIs of the estimates
of the effectiveness of the intervention and the vaccines. The measure of
effectiveness was the difference in rates (vaccination rates in the case of
the intervention and incidence rates of the illnesses in the cases of the
vaccines), and the upper and lower bounds in effectiveness were based on the
CI for the difference in rates. Values of effectiveness of the intervention
and the vaccines used in the base case, lower bound, and upper bound estimates
are listed in Table 1. The choice
of these values is justified in the following subsections.
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Table 1. Point Estimates and Confidence Intervals for the Effectiveness
of the Intervention to Promote the Pneumococcal and Influenza Vaccines and
the Effectiveness of the Vaccines
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We performed 3 sets of estimates based on 3 sets of CIs: (1) the effectiveness
of the intervention, (2) the effectiveness of the vaccine, and (3) the effectiveness
of the intervention and the vaccine. For example, the lower bound of the quasi-CI
of the first set of estimates was calculated by means of the upper bound of
effectiveness of the intervention.
Values of other variables and their sources are listed in Table 2. For many variables, a 1-way sensitivity analysis in which
the values were changed within reasonable bounds did not change the cost-effectiveness
ratio by more than $1000. Examples include the cost of the vaccines, the frequency
of influenza epidemic years, and probability of a bed-disability day from
influenza and pneumonia. These variables are identified with an asterisk in Table 2. For other variables, changing
the values would substantially change the cost-effectiveness ratio. These
variables include the discount rate; the cost of the intervention, for which
the 1-way sensitivity analyses are reported; and the incidence of and mortality
rate from bacteremia. (See the "Comment" section.)
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Table 2. Values of Other Variables Used in the Cost-effectiveness
Model
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Effectiveness of the Community-Based Outreach Initiative to Promote
the Pneumococcal and Influenza Vaccines
The point estimate and the CIs for the effectiveness of the intervention
were obtained from the randomized controlled trial. The measure of effectiveness
was the difference in vaccination rates between the intervention and control
groups; for the vaccination rates, please see Krieger et al.20
The trial showed that the effectiveness varied by vaccine and by prior immunization
status, so we performed 2 sets of estimates for the cost-effectiveness: (1)
one set for the intervention as implemented and (2) one set for an intervention
that would be targeted to people who had never received the pneumococcal vaccine
or who did not receive the influenza vaccine in the previous year. For the
reference case of the first set of estimates, the intervention was 15% effective
in promoting the pneumococcal vaccine and 6% effective in promoting the influenza
vaccine. For the second set, the intervention was 21% effective in promoting
the pneumococcal vaccine and 27% effective in promoting the influenza vaccine.
The second set of estimates embodies the assumption that the effectiveness
of the intervention for those subsamples could be extended to a sample as
large as the full sample in a targeted outreach initiative.
Effectiveness of the Pneumococcal Vacine Against Pneumococcal Bacteremia
Estimates of effectiveness and CIs were based on a case-control study37 in which a significant negative relationship was
found between effectiveness of the vaccine and number of years since vaccination
and between effectiveness and patient's age. Using those data, Sisk et al10 estimated a declining, linear relationship between
effectiveness and immunity during a 6-year period for 3 age strata: 65 to
74 years, 75 to 84 years, and 85 years or older. For the reference case, we
assumed that effectiveness was the weighted average of the 65- to 74-year
and 75- to 84-year age strata reported by Sisk et al,10
where the weights were the numbers of people in each 10-year age interval
in the stationary population.30 We used the
average for these 2 strata because the average age of the participants of
the trial was 75 years.20 Only a few participants
were aged 85 years and older, and the available evidence suggested that the
vaccine was not effective for people aged 85 years or older.37
Note that the outcome measure reported by Shapiro et al37
and Sisk et al10 was incidence of pneumococcal
bacteremia, and we assumed that their estimates could be applied to hospitalizations
and mortality.
Effectiveness of the Influenza Vaccine
The point estimate and CI were based on the randomized controlled trial
of the efficacy of the influenza vaccine among people aged 60 years and older
in whom the vaccine reduced the incidence of influenza by 50%.31
For the reference case estimate, we assumed that the vaccine reduced disability
days, outpatient visits, hospitalizations, and mortality by 50%. Although
the outcome measure of the trial was incidence of influenza, this estimate
was within the range of estimates from case-control studies for the effectiveness
of the vaccine in reducing hospitalizations12, 38, 39
and mortality.12, 38, 40
DISCOUNT RATE
We followed the recommendations of the Panel on Cost-effectiveness in
Health and Medicine and discounted all future costs and benefits in the reference
case by 3%.21 The discount rate reflects the
fact that people prefer to receive benefits and save costs in the present
relative to the future. Also, in accord with their recommendations, we conducted
a 1-way sensitivity analysis of the CEA with the use of a discount rate of
5%.
COST OF THE COMBINED, COMMUNITY-BASED OUTREACH INITIATIVE TO PROMOTE
THE PNEUMOCOCCAL AND INFLUENZA VACCINES
The main elements of the intervention were the letter reminders, computer
system for tracking vaccine status, volunteer training, and telephone calls
to seniors who were not immunized. Consequently, the estimate of the cost
of the intervention focused on those elements and excluded the cost of the
on-site vaccinations and announcements at senior center activities that were
available to both the intervention and control groups. The analysis also excluded
research costs associated with conducting the randomized, controlled trial.
There were 5 categories of costs of the intervention: (1) staff, (2) volunteers,
(3) advisory committee, (4) computer tracking system, and (5) materials. Sources
of data and assumptions for the first 3 categories are described below. The
computer tracking system and materials were valued at their purchase prices,
and the cost of the computer tracking system was amortized over 5 years.
Staff at the senior center and Public Health kept records of the time
spent on the project, either on time sheets designed for the project or on
their personal calendars. Their time was valued at their salary plus benefits.
As recommended,41 the estimates also included
a 7% markup for general overhead, which is the overhead rate for Public Health.
We estimated that 37.5% of all time at meetings was devoted to the intervention,
based on interviews with the staff.
Volunteers also kept records of the amount of time they spent calling
seniors who were not vaccinated, either on time sheets designed for the project
or on senior center records. The senior center kept good records of volunteer
contributions because much of the budget depended on matching funds. To conform
to the reference case, their time was valued at the mean weekly earnings of
people aged 65 years and older36 divided by
40, which was $9.80 per hour. (Earning data by sex were not available for
this age group.) The estimated wage was based on the assumption of a 40-hour
work week, which may not have been valid for people aged 65 years and older
because it is an age that is associated with retirement. To check the validity
of this estimate, we also collected primary data from participants about work
outside the home and hourly wages as part of surveys before and after the
intervention. The estimated wage was identical to the average hourly wage
of the participants.
The advisory committee costs were somewhat specific to community-based
interventions because of the time and effort required to establish trust among
community members, health agencies, and researchers. We used sign-in sheets
to track time spent at meetings. Their time was valued at $9.80 per hour for
members of the senior center and at salary plus benefits for representatives
of health agencies and researchers. We estimated that 37.5% of the time at
meetings was devoted to the intervention.
The estimated total cost of the intervention was $25 076. The cost
of each of the 5 categories are reported in Table 3. As shown, $22 523 or 90% of the total cost, was for
personnel. Seventy-seven percent of total cost was for staff at the senior
center and Public Health, 10% for volunteers, and 3% for the advisory committee.
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Table 3. Cost of the Community-Based Outreach Initiative to Promote
the Pneumococcal and Influenza Vaccines
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We also projected that the intervention could be replicated for about
$19 315 on the basis of lessons learned during the first year of implementation.
Those lessons included (1) hiring a project coordinator to work full-time
for 6 weeks during the outreach initiative rather than part-time for 5 months
and (2) eliminating the computer tracking system, because it was just as efficient
to record the information manually.
INFORMED CONSENT
All protocols for the randomized controlled trial of the vaccine to
promote the vaccines were approved by the University of Washington Human Subjects
Protection Division, Seattle, and informed consent was obtained from each
participant.
RESULTS
Beginning with the reference case results, Table 4 reports the total cost and total effectiveness for the intervention
group and the control group, as well as marginal cost, marginal effectiveness,
and cost-effectiveness ratio for 6 estimates. The first 3 estimates in the
top half of the table were for the combined outreach initiative, pneumococcal
vaccine, and influenza vaccine as implemented. The ratio of the intervention
as implemented was $35 486 per QALY for the combined outreach initiative,
whereas it was $53 547 per QALY for the pneumococcal vaccine and $130 908
per QALY for the influenza vaccine. As shown, the marginal effectiveness of
the pneumococcal vaccine was greater than that of the influenza vaccine, reflecting
the relatively greater effect of the intervention on pneumococcal vaccine
coverage than influenza vaccine coverage. The marginal effectiveness of the
combined outreach initiative was the sum of the independent analyses (aside
from rounding error), because combined outreach did not alter the effectiveness
of the intervention or the vaccines. The marginal cost was roughly the same
for all 3 estimates, because the cost of the intervention was the same for
all of them.
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Table 4. Cost and Effectiveness Results for the Reference Case
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The 3 estimates in the bottom half of the table were for the combined
outreach initiative, pneumococcal vaccine, and influenza vaccine if the intervention
could be targeted to seniors who had never received a pneumococcal vaccine
or who had not received the influenza vaccine in the previous year. For each
of these estimates, the marginal costs were lower and the marginal effectiveness
was higher than in the estimates for the intervention as implemented. The
cost-effectiveness ratios were $11 771 per QALY for the combined outreach
initiative, $38 030 per QALY for the pneumococcal vaccine, and $22 431
per QALY for the influenza vaccine.
The quasi-CIs estimated from the partial stochastic analyses are reported
in Table 5. For the intervention
as implemented, the quasi-CI of the pneumococcal vaccine that was calculated
from the CI of effectiveness of the intervention ranged from $37 305
to $82 364 per QALY. The interval that was calculated from the CI of
effectiveness of the vaccine ranged from $40 498 to $144 380 per
QALY. The range was greater for the latter, because the CI of effectiveness
of the vaccine was not symmetric and the lower bound of effectiveness of the
vaccine was less than 50% for 5 of 6 years. Finally, the interval that was
calculated jointly from CIs of effectiveness of the intervention and the vaccine
ranged from $27 944 to $218 750 per QALY. The range of the quasi-CI
that was calculated jointly was greater than the sum of the ranges calculated
independently, because the effectiveness of the vaccine had a multiplicative
rather than an additive effect.
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Table 5. Quasi–Confidence Intervals Estimated in Partial Stochastic
CEA*
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For the intervention as implemented, the quasi-CI of the influenza vaccine
that was calculated from the CI of effectiveness of the intervention ranged
from $67 666 to $409 553 per QALY. The interval that was calculated
from the CI of effectiveness of the vaccine ranged from $98 179 to $171 428
per QALY. The range was greater for the former, because the lower bound of
the CI of effectiveness of the intervention was only 2% and the denominator
of that ratio was relatively small. Finally, the interval that was calculated
jointly from the CIs of effectiveness of the intervention and the vaccine
ranged from $49 606 to $528 852 per QALY.
For the intervention as implemented, the quasi-CI of the combined outreach
initiative that was calculated jointly from the CIs of effectiveness of the
intervention and the vaccines ranged from $15 145 to $152 311 per
QALY. For the targeted intervention, the quasi-CI of the combined iniatiative
that was calculated jointly ranged from $3330 to $46 095 per QALY.
In a 1-way sensitivity analysis using a 5% rather than a 3% discount
rate, the cost-effectiveness ratio of the combined outreach initiative was
$40 830 per QALY for the intervention as implemented, and $13 428
per QALY for the targeted intervention. The higher discount rate increases
the ratios, because it decreases the value of the future benefits in the denominator
and it decreases the value of future cost savings in the numerator.
In a 1-way sensitivity analysis using $19 315 as the projected
cost of replicating the intervention, the cost-effectiveness ratio for the
combined outreach initiative was $26 512 per QALY for the intervention
as implemented and $7843 per QALY for the targeted intervention.
COMMENT
The CEA demonstrated that the combined community-based outreach initiative
to promote the pneumococcal and influenza vaccines had a lower cost per QALY
and a narrower quasi-CI than an intervention to promote either vaccine alone.
As implemented, the cost-effectiveness ratio of the combined outreach initiative
was $35 486 per QALY, whereas it was $53 547 per QALY for the pneumococcal
vaccine and $130 908 per QALY for the influenza vaccine. The merits of
the combined outreach initiative were even more evident when we assessed the
uncertainty of the estimates.
There is no single criterion of a cost-effectiveness ratio below which
an intervention should be adopted. The US Panel on Cost-effectiveness in Health
and Medicine recommended comparisons relative to other interventions,42 as presented in the preceding paragraph. As an alternative
comparison, note that the median cost-effectiveness ratio of preventive interventions
surveyed at the Harvard Center for Risk Analysis was $47 590# per QALY,43 and the cost-effectiveness ratio of the combined
outreach initiative was lower than that median.
Canadian experts classified interventions into 3 categories by their
cost-effectiveness ratios: (1) less than $28 000# per QALY, (2) $28 000#
to $140 000# per QALY, and (3) more than $140 000# per QALY.44, 45 A ratio in the first category was
strong evidence for adoption of an intervention. A ratio in the second category
was moderate evidence for adoption of an intervention; some interventions
in the second category were routinely provided and others were not. A ratio
in the third category was weak evidence for adoption. According to their categories,
the combined outreach initiative, as well as independent interventions for
the pneumococcal and influenza vaccines, would be in the second category of
cost-effectiveness ratios. Considering the uncertainty of the estimates, however,
the quasi-CI of the combined outreach initiative ($15 145 to $152 311
per QALY) was more or less within the second category, whereas the quasi-CIs
of an intervention for only the pneumococcal vaccine ($27 944 to $218 750
per QALY) was between the second and third categories and an intervention
for only the influenza vaccine ($49 606 to $528 852 per QALY) was
mostly in the third category.
The analysis also demonstrated that the cost-effectiveness ratio could
be reduced by targeting the intervention or lowering the cost of the intervention.
The cost-effectiveness ratio of a combined outreach initiative targeted to
people who had never received the pneumococcal vaccine or who had not received
the influenza vaccine in the previous year was $11 711 per QALY, with
a quasi-CI of $3330 to $46 095 per QALY, which was more or less within
the first category of interventions. For the intervention as implemented,
participants were selected from a list of people aged 65 years and older who
lived in specific ZIP code areas. For the targeted intervention, Medicare
could provide a list of people for whom claims had been submitted for the
pneumococcal and the influenza vaccines each year, and participants could
be selected from the list of people aged 65 years and older who were not on
the Medicare list in 2 previous years for the pneumococcal vaccine or the
previous year for the influenza vaccine. Alternatively, managed care plans
and physicians could report lists of patients who received the vaccines each
year, and participants could be selected from the list of people aged 65 years
and older who were not on the managed care plan and physician list. Note that
the cost of the intervention reported above did not include the cost of identifying
people for the targeted intervention.
Finally, the CEA of the combined, community-based outreach initiative
highlighted the importance of evaluating interventions to promote vaccines
and other preventive care. The CEA of the pneumococcal vaccine showed that
it was cost saving,10 and CEAs of the influenza
vaccine suggested that it was cost saving or that the net cost per vaccine
was about $7#.11, 12, 13, 14
Promoting the vaccines however, was costly, especially among urban, underserved
communities. When the cost of the intervention to promote the vaccines was
included, even the combined outreach initiative was in the second category
of cost-effectiveness ratios44 rather than
being cost saving.
There were some limitations to the CEA, which we note below. The CEA
did not include a 1-way sensitivity analysis with the unrelated medical costs
of survivors. The US Panel on Cost-effectiveness in Health and Medicine concluded
that the reference case may exclude these costs, but a researcher should conduct
a 1-way sensitivity analysis whenever he or she believes that including them
may make a significant difference to the analysis.21
Meltzer46 demonstrated that the CEA should
include all future medical and nonmedical costs and provided a method of estimating
the bias from omitting them. Using Meltzer's estimate of the medical expenditures
for a 75-year-old, we estimated that omitting unrelated medical costs of survivors
reduced the cost-effectiveness ratios by $11 000. The bias primarily
reflected the lower value of average health measured in QALYs among seniors
(0.71 on a scale from 0 to 1) and was essentially the same for the combined
outreach initiative, pneumococcal and influenza vaccines. Similarly, Sisk
et al10 reported that including unrelated medical
costs increased the cost-effectiveness ratio of the pneumococcal vaccine by
$9600# and $12 900# in the base-case analysis of people 65 to 74 years
old and 75 to 84 years old, respectively. Using Meltzer's estimate of the
present value of future net resource use per year of life saved for a 75-year-old,
we estimated that omitting all future costs reduced the cost-effectiveness
ratios in our study by $24 000.
As noted earlier, the cost-effectiveness ratios for the pneumococcal
vaccine and the combined outreach initiative were sensitive to changes in
the values of the incidence of and mortality from bacteremia. Unfortunately,
the only available evidence was from community-specific studies, because there
was no nationwide surveillance for pneumococcal bacteremia.47
We used the base-case values from Sisk et al10
so that our estimates could be compared with estimates that focused only on
the costs of the vaccine. Note, however, that the value of the incidence of
bacteremia we used was on the upper end of the range of available estimates,
whereas the value of mortality from bacteremia was in the middle of the range
of available estimates.
The CEA did not include the effect of the pneumococcal vaccine against
pneumococcal pneumonia, because the vaccine's effectiveness among people aged
65 years and older is controversial. A meta-analysis of randomized controlled
trials showed that the pneumococcal vaccine was not effective against pneumococcal
pneumonia for high-risk patients, but it raised the possibility that immunocompetent
elderly people should not be characterized as high risk.25
Future research that focuses on the immunocompetence of the elderly rather
than on their risk of infection may show that the pneumococcal vaccine is
effective against pneumococcal pneumonia among the immunocompetent elderly.
Such evidence would reduce the cost-effectiveness ratio for the pneumococcal
vaccine and the combined outreach initiative.
Finally, the value of the effectiveness of the influenza vaccine on
mortality in our estimates was limited to mortality from pneumonia and influenza.
Again, we chose this approach so that our estimates could be compared with
previous research that focused only on the costs of the vaccine.14
This approach assumed that most of the illness attributed to influenza during
an epidemic would be reported with diagnostic codes for pneumonia and influenza.
There was evidence from case-control studies, albeit mixed, that the influenza
vaccine affected mortality from other causes in addition to pneumonia and
influenza. The vaccine significantly reduced mortality from all causes12 and hospital deaths from all causes38
among elderly people living in the community. Mullooly et al,11
however, reported that the influenza did not significantly reduce hospital
deaths among high-risk elderly living in the community. Limiting the effectiveness
to mortality from pneumonia and influenza could represent an upward bias in
the cost-effectiveness ratio.
CONCLUSIONS
The community-based outreach initiative to promote the pneumococcal
and influenza vaccines was reasonably cost-effective at $35 486 per QALY.
Further improvements in cost-effectiveness could be made by targeting the
intervention to people who had never received the pneumococcal vaccine or
who had not received the influenza vaccine in the previous year. Lessons learned
during the first year of implementation would also reduce the cost of the
outreach initiative in subsequent years.
AUTHOR INFORMATION
Accepted for publication July 28, 2000.
This research was funded by the US Centers for Disease Control and Prevention,
Atlanta, Ga, cooperative agreement U50/CCU011820-02 (Urban Research Centers),
and United Way of King County, Seattle, Wash.
We thank Carol Allen and Bob Burnside of the Central Area Senior Center,
the senior volunteers, and the Project Advisory Group (Russ Alexander, MD,
MPH, Ross Burks [deceased], Eric Coleman, MD, MPH, Mary Davis, Seawellow Holland,
Peter Houck, MD, MPH, Tom Koepsell, MD, MPH, Rachel Pitts, RN, BSN, and Pamela
Owens-Williams, MSW) for their generous contributions to this project. We
also thank the anonymous reviewers of this article.
From Public Health: Seattle & King County, Seattle, Wash (Drs Weaver
and Krieger and Ms Ciske); Departments of Health Services (Drs Weaver and
Krieger), Medicine (Dr Krieger), and Psychosocial and Community Health Nursing
(Ms Ciske) and Nursing School (Ms Walls), University of Washington, Seattle;
and Northeast Health Care Quality Foundation, Dover, NH (Dr Castorina).
Corresponding author: Marcia Weaver, PhD, MA, 937 Broadway Ave E,
Seattle, WA 98102 (e-mail: mweaver{at}u.washington.edu).
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