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Pneumococcal Vaccination
Analysis of Opportunities in an Inner-city Hospital
Shahid Husain, MD;
David Slobodkin, MD, MPH;
Robert A. Weinstein, MD
Arch Intern Med. 2002;162:1961-1965.
ABSTRACT
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Background Adult pneumococcal vaccination rates for persons at risk of developing
pneumococcal disease remain below desired levels. Various sites within the
hospital (inpatient medicine wards [IMWs], general medicine clinics [GMCs],
and emergency departments [EDs]) have been suggested as venues for administering
vaccination. The cost-effectiveness of such sites for delivery of pneumococcal
vaccination is not known.
Objective To compare the potential coverage of at-risk patients and cost of pneumococcal
vaccination delivered in an ED, GMC, and IMWs.
Methods We studied a retrospective cohort of 300 patients with pneumococcal
bacteremia who had been hospitalized at Cook County Hospital, an inner-city
Chicago public teaching hospital, from January 1994 through December 1998.
We measured the presence of risk factors, as defined by the Centers for Disease
Control and Prevention, for developing pneumococcal disease prior to index
admission for bacteremia; patient use of ED, GMC, and IMWs from 4 weeks to
5 years before index admission; size of target population for vaccination
in each site; and cost benefit of a pneumococcal vaccination strategy at each
site.
Results In the 4 weeks to 5 years before index admission, risk factors were
present in 209 patients; 182 (87.1%) of the 209 had been in the ED, 104 (49.7%)
in an IMW, and 64 (30.6%) in a GMC. The ED showed the greatest potential vaccine
coverage, at a cost savings in a best-case scenario; the IMWs showed the best
cost-benefit ratio but would provide access to fewer at-risk patients; and
a program in the GMC would reach the fewest at-risk patients, with a cost-benefit
ratio similar to that of the ED.
Conclusions The ED in an inner-city hospital has the potential to vaccinate more
patients at risk of pneumococcal bacteremia than a GMC or IMWs, and may do
so at a cost savings. A prospective evaluation of such a strategy is warranted.
INTRODUCTION
PNEUMOCOCCAL bacteremia is a major cause of morbidity and mortality
in the United States, with a yearly incidence estimated to be 15 to 30 cases
per 100 000 population.1 This vaccine-preventable
disease kills more Americans than all other vaccine-preventable diseases combined,
in large part because of inadequate rates of vaccination among populations
at risk.
Fedson and Baldwin2 and Fedson and Chiarello3 reported that 36% to 70% of patients hospitalized
for pneumococcal bacteremia had been inpatients at the same hospital during
the previous 5 years. This suggested that vaccination at the time of hospital
discharge for patients with risk factors for pneumococcal bacteremia might
prevent subsequent morbidity and mortality. A significant percentage of patients
hospitalized with pneumococcal bacteremia also had been seen previously in
the hospital's outpatient clinic, suggesting a role for vaccination programs
in this setting as well.4 More recently, Stack
et al5 demonstrated that 55% of patients hospitalized
in a university hospital had visited that hospital's emergency department
(ED) during the previous 5 years, and Slobodkin et al6-8
demonstrated that immunizing patients against pneumococcal disease during
visits to a public hospital ED was feasible.
Considering the large number of patient visits in our public hospital
ED, we hypothesized that an ED-based vaccination program could capture a majority
of at-risk patients in a cost-effective manner. We tested this hypothesis
by doing a retrospective review of patients with pneumococcal bacteremia and
by comparing vaccination opportunities and costs in our ED, general medicine
clinic (GMC), and inpatient medicine wards (IMWs).
METHODS
This study was conducted at Cook County Hospital, a large inner-city
public hospital in Chicago, Ill. We reviewed microbiology laboratory records
from January 1, 1994, to December 31, 1998, to identify all adult patients
with blood cultures positive for Streptococcus pneumoniae. The laboratory routinely serotypes pneumococcal isolates using diagnostic
antisera of the Statens Serum Institut (Copenhagen, Denmark). Serotypes were
recorded for each positive culture. Patient records and computerized discharge
summaries were reviewed to determine demographic information, pneumococcal
vaccination status, and presence of risk factors for the development of pneumococcal
disease and indications for pneumococcal vaccination. The reviews included
each prior contact with the institution's GMCs, ED, and/or IMWs during the
period from 4 weeks to 5 years before the onset of each bacteremic episode.
Contacts within this time frame were defined as opportunities to immunize.
We report the costs in 1998 dollars. Annual hospital admissions and
ED and clinic visit data represent the 1998 hospital census. We used our hospital's
annual expenditure report to estimate the local cost of a pneumococcal vaccination
program and the potential cost savings in this patient population. The cost
of purchasing and administering pneumococcal vaccine in our hospital was $15
per dose.6, 8 The average cost
of 1 day of hospitalization was $1178, with a one-time administrative admission
cost of $689 (unpublished data, 1998).9
The percentage of at-risk patients in the ED was adapted from prior
studies.6-8 The
percentage of at-risk patients in the GMC was derived from surveys of clinic
patients. Our IMW analyses are limited to the medicine service because only
10 patients with bacteremia had prior admissions to other services. The percentage
of patients with risk factors for pneumococcal disease on the IMWs was determined
by a prospective survey of 382 consecutive admissions. The cost of a vaccination
program at each site was calculated by multiplying the cost of vaccination
per patient by the number of at-risk patients at that site.
The number of patients with potential benefit from pneumococcal vaccination
was calculated by multiplying the number of patients with bacteremia and risk
factors that warranted vaccination by the percentage infected with strain
types in the pneumococcal vaccine by the efficacy (0.45-0.85) of the current
pneumococcal vaccine.1 The cost of care of
patients with potential benefit from vaccination was estimated by multiplying
the number of these patients by the average length of hospital stay for our
patients with bacteremia (11.83 days) by the cost of hospitalization per day.
A cost-benefit ratio was obtained by dividing the cost of vaccination for
the total at-risk patient population by the cost of index hospitalization
for those patients with bacteremia who had potential benefit from vaccination.
Data were analyzed using SPSS version 8.0 (SPSS Inc, Chicago, Ill).
The  2 statistic was used to determine the significance of
nominal variables. All reported P values are 2-tailed.
RESULTS
We identified 325 bacteremic episodes in patients older than 16 years.
The source patient could not be identified for 10 of these episodes owing
to incomplete or corrupted identifiers. The remaining 315 bacteremic episodes
occurred in 300 unique patients; 287 patients had a single episode, 11 patients
had 2 episodes each, and 2 patients had 3 episodes each. For patients with
more than 1 bacteremic episode, only the initial episode was analyzed.
Most (69.6%) of our patients (n = 209) had risk factors for the development
of pneumococcal disease at the time of a prior hospital contact (Table 1); 154 (74%) of the 209 patients
had at least 2 risk factors (Table 2).
Only 17 (22%) of the 77 patients with human immunodeficiency virus (HIV) had
this as their only risk factor. Among the 37 patients 65 years or older, the
most common additional risk factors were diabetes (n = 17; 46%), heart failure
(n = 12; 32%), and chronic renal failure (n = 10; 27%). In the 172 patients
younger than 65 years who had risk factors, HIV/acquired immunodeficiency
syndrome (AIDS), alcohol abuse, and chronic renal failure constituted 67%
of risk factors.
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Table 1. Frequency of Risk Factors in 300 Patients With Pneumococcal
Bacteremia*
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Table 2. Demographics of 300 Patients With Pneumococcal Bacteremia
Admitted to Cook County Hospital, January 1994 Through December 1998
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Overall mortality in our cohort of patients with bacteremia was 8% (Table 2). The mortality rate was 3 times
higher in patients with any risk factors than it was in those with no risk
factors (10.0% vs 3.2%; P = .05). Lengths of stay
for patients with and without risk factors were similar (12.4 and 11.8 days,
respectively), although this is confounded by the difference in mortality
rates.
Capsular types included in the commercially available 23-valent pneumococcal
vaccines (Merck Pneumovax 23 and Lederle Labs Pnu-Imune 23) caused 93% of
bacteremias. The most prevalent capsular types in our patients with bacteremia,
in descending order of frequency, were 9, 4, 19, and 14. There were no differences
in the frequency of serotypes by different sites of prior hospital contact
(ie, ED, GMC, or IMWs). Only 4 of 100 patients with risk factors for whom
complete vaccination records were available were documented to have pneumococcal
vaccination, 2 prior to the index admission (1 patient's subsequent infection
was with a strain type represented in the 23-valent vaccine) and 2 at discharge
from the index admission.
Almost all (n = 198; 95%) of the 209 patients with risk factors had
contact with Cook County Hospital 4 weeks to 5 years before their index admission
for pneumococcal bacteremia (Table 3).
These prior contacts included a median of 2 ED visits, 5 GMC visits, and 1.5
IMW admissions. If all at-risk patients would have received pneumococcal vaccination
at a prior contact, the patients in 182 of the 209 bacteremic episodes would
have been immunized by a program in the ED; 104 would have been immunized
by a vaccination program that focused on hospital discharge; and 64 would
have been immunized by a program in the GMC (Table 3). Conversely, vaccination efforts conducted solely in the
inpatient setting would have failed to vaccinate 105 of our 209 patients with
risk factors for pneumococcal bacteremia, and a program in the GMC would have
missed 145 patients, while an ED-based program would have missed only 27 patients.
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Table 3. Summary of Prior Hospital Admissions, Clinic Visits, or Emergency
Department Visits From 4 Weeks to 5 Years Before the Index Admission for Pneumococcal
Bacteremia in 209 Patients With 1 or More Risk Factors for Pneumococcal Disease
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Table 4 outlines projected
benefits and direct costs based on vaccination programs at different administrative
sites in the hospital: 15 to 28 bacteremic episodes per year might have been
prevented by a vaccination program in the ED, 5 to 10 by a program in the
GMC, and 9 to 17 by a program based at hospital discharge. These results assume
100% vaccination of the large at-risk target populations seen at each of these
sites. The inpatient discharge vaccination strategy seems most cost-effective
(Table 4) but would reach fewer
at-risk patients than would an ED-based program; moreover, all but 1 patient
admitted to the hospital had prior contact with the ED or GMC. In a best-case
scenario, an ED-based program could show direct cost savings of $87 174
per year ($447 174 minus $360 000).
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Table 4. Comparison of Projected Yearly Direct Cost and Benefit in
3 Venues of Pneumococcal Vaccination Programs, Cook County Hospital, 1994
Through 1998
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COMMENT
Pneumococcal vaccination rates in the United States are reported to
be 28% to 47%, well below the desired 90% levels,10
with the result that many patients are denied effective protection against
this major cause of morbidity and mortality. Our study demonstrates that an
ED-based vaccination strategy would protect most patients at risk for pneumococcal
bacteremia in an inner-city public hospital, with a best-case scenario showing
cost savings.
Our study supports and extends prior analyses of hospital pneumococcal
vaccination programs5-8
in several ways. The lengths of stay and mortality rate for our patients with
bacteremia and the percentage of our ED patients with risk factors for vaccination
are very similar to those noted by Stack and colleagues.5
As in that study, our economic calculations are based on a hospital perspective;
we had additional details available for our cost-benefit analysis. We compared
3 different venues within the hospital: the ED, the GMC, and IMWs. We studied
a public hospital where episodic care in the ED, for a very large number of
at-risk patients, is common. Our analysis includes a range of vaccine efficacy
rates and the percentage of vaccine capsular types in patients with pneumococcal
bacteremia in our institution.
For several reasons, an ED-based pneumococcal vaccination study may
be particularly warranted. There were more than 100.4 million ED visits in
the United States in 1998.11 The ill, the elderly,
the poor, and members of ethnic minorities are overrepresented in that group.12-13 These patients are at higher risk
of respiratory disease and of undervaccination. Although significant progress
has been made in the last 10 years in immunizing Medicare patients overall,
vaccination rates among black and Hispanic Medicare patients lag significantly
behind those of the general Medicare population.10, 14
Also, estimates of vaccination rates among chronically ill patients younger
than 65 years show that this group has benefited little. Known ethnic discrepancies
in access to medical insurance and medical care15-16
suggest that chronically ill minority patients younger than 65 years may have
the lowest vaccination rates of any group.
The existence of disparities in pneumococcal vaccination rates points
out the need to intensify vaccination efforts in settings with high proportions
of minority underinsured or uninsured patients. Emergency departments are
frequently visited by such patients, including America's 41 million uninsured,
who have little or no access to other medical practitioners.17
However, successful ED-based pneumococcal vaccination programs seem to be
rare. Critics of such programs cite the variable efficacy of this vaccine,
the perceived indifference of patients and ED physicians to participate in
such programs, and cost and time constraints as barriers to an effective ED
vaccination program. Nevertheless, surveys of ED patients and physicians suggest
that at least half of those queried would accept and participate in such a
program.18-19 A pilot study in
our ED showed that the median extra time for screening and pneumococcal vaccination
was only 4 minutes per patient (range, 2-10 minutes) without deployment of
additional personnel and that 76% of high-risk patients who were screened
accepted and received pneumococcal vaccination.7
The other major arena for pneumococcal vaccination, which has been suggested
but largely ignored, is the inpatient setting. Fedson and Baldwin2 and Fedson and Chiarello3
have shown that more than two thirds of patients with pneumococcal bacteremia
had previous hospital admission, but the percentage of hospitalized patients
who have risk factors that would make them vaccine recipients and the hospital
discharge vaccination rates remain largely unknown. Our study shows the relatively
low cost associated with immunizing at-risk individuals at discharge from
IMWs. The use of a standing-order program, as recommended recently by the
Advisory Committee on Immunization Practice,10
is a strategy that could be applied effectively in this setting.
There are certain limitations of our study that warrant consideration.
Our reviews were retrospective, and the charts may not have had complete information
regarding risk factors and vaccination status. The percentage of bacteremias
in our patients due to strain types present in the 23-valent pneumococcal
vaccine is slightly higher than the 86% reported recently, but this would
not affect the comparison of venues for vaccination. All cost analyses were
from a hospital perspective; however, our findings are comparable to an analysis
from a Medicare20 perspective (data not shown).
The cost of hospitalization in our public hospital may be less than at other
institutions, and our ratio of fixed and variable costs may be different,9 which would tend to underestimate the cost savings
of a vaccination program. Also, the setting of this study in a public hospital,
where uninsured are overrepresented, might not completely represent the situation
in community or private hospitals, where sites such as clinics or private
offices may have a larger role in a vaccination program and where indirect
societal benefits of vaccination (eg, a healthier workforce) might be greater.
We did not include the cost of developing the vaccination program in
our calculations, but we believe that such costs would be similar in each
of the venues; the cost-benefit ratios (Table 4) are directly proportional to changes in costs of vaccine
and its administration. We did not evaluate the effects of patients' repeated
ED, GMC, or IMW visits, which would tend to lessen costs and increase the
likelihood of vaccinating at-risk individuals. Repeated visits also carry
the potential for inadvertent repeated vaccination. Although the risks posed
by revaccination are small,10 the movement
to electronic medical records could alleviate this problem. In the meantime,
ED records can be adapted to readily retrieve vaccination status.6, 8 Finally, the high percentage of patients
with HIV/AIDS in our case series might affect our cost-benefit calculations,
although most of our HIV-infected patients had other indications for vaccination,
and only a small proportion had full-blown AIDS. While questions have been
raised about the efficacy of pneumococcal vaccine in patients with HIV/AIDS,21 the Centers for Disease Control and Prevention recommends
that all patients with HIV be vaccinated, and in the era of highly active
antiretroviral therapy, the improved immunologic status of patients with HIV
may make pneumococcal vaccine more efficacious.
In conclusion, our findings suggest that an ED-based pneumococcal vaccination
program in an inner-city hospital can reach a larger number of underserved
patients at risk of pneumococcal bacteremia than the other venues evaluated.
The relative importance of such a program compared with other possible ED
health promotion initiatives—screening for asymptomatic sexually transmitted
diseases and HIV, smoking cessation counseling, domestic violence evaluation—depends
on analysis of local disease morbidity, program feasibility, likelihood of
program benefit, and the possibility of bundling such value-added services
for high-risk patients. Nevertheless, with increasing rates of antibiotic
resistance in pneumococci, a prospective evaluation of the impact of an ED
pneumoccocal vaccination program seems warranted.
AUTHOR INFORMATION
Accepted for publication February 6, 2002.
We thank Frank E. Kocka, PhD, and the staff of the Cook County Hospital
Clinical Microbiology Laboratory for their expertise.
Corresponding author: Robert A. Weinstein, MD, Division of Infectious
Diseases–129 Durand, Cook County Hospital, 1835 W Harrison St, Chicago,
IL 60612 (e-mail: rweinste{at}rush.edu).
From the University of Pittsburgh Medical Center, Pittsburgh, Pa (Dr
Husain); School of Public Health, University of Illinois at Chicago (Dr Slobodkin),
and Cook County Hospital and Rush Medical College (Dr Weinstein), Chicago,
Ill.
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RELATED LETTER
Corrections to Table
Shahid Husain, David Slobodkin, and Robert A. Weinstein
Arch Intern Med. 2004;164(5):573.
EXTRACT
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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
Lessons learned from inpatient vaccination in michigan.
Winston et al.
American Journal of Medical Quality 2006;21:125-133.
ABSTRACT
Corrections to Table
Husain et al.
Arch Intern Med 2004;164:573-573.
FULL TEXT
A Vaccine-Preventable Infection -- So What's the Problem?
JWatch Infect. Diseases 2002;2002:5-5.
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