Rabies Postexposure Prophylaxis -- Connecticut, 1990-1994

In Connecticut, the first case of animal rabies associated with the ongoing raccoon rabies epizootic was identified in March 1991; since then, cases of animal rabies have been confirmed in all eight counties of the state. Because of heightened awareness of the potential for rabies and the nearly always fatal outcome of this disease, the numbers of persons in Connecticut receiving rabies postexposure prophylaxis (PEP) was suspected to have increased substantially during 1990-1994. In Connecticut, PEP is administered with pharmaceuticals obtained through retail channels. In 1994, the Connecticut Department of Public Health surveyed Connecticut hospitals and the two pharmaceutical manufacturers that produce human rabies immunoglobulin (HRIG) to estimate the number of persons receiving PEP during 1990-1994 * and the costs associated with treatment. This report summarizes the survey findings, which suggest an increasing trend in the administration of PEP in Connecticut corresponding with the statewide spread of raccoon rabies.

In October 1994, a questionnaire was mailed to the pharmacy director at each of the 33 acute-care hospitals in Connecticut. The questionnaire asked about rabies vaccine and HRIG, including the number of vials used each year during 1990-1994 and the amount charged for each vial. Questionnaires were returned from 32 (97%) of the 33 hospitals. Because of limitations in the maintenance of inventory records, only 9-15 (28%-47%) hospitals were able to provide information about the amount of HRIG used for any period before 1994.

At the time of the survey, all 32 hospitals reported stocking vaccine, and 31 (97%) also stocked HRIG. Charges to patients for these products varied widely (Table_1). In 1994, the median estimated cost for HRIG and rabies vaccine for a person weighing 165 lbs (i.e., 10 mL HRIG and five vaccine doses) was $1498 (range: $787-$4548) and for a child weighing 33 lbs (i.e., 2 mL HRIG and five vaccine doses) was $1127 ($481-$3371).

Because most hospital pharmacies do not monitor the number of patients who receive rabies PEP, the amount of HRIG dispensed by the hospital pharmacies was used as a surrogate measure of the number of treatments initiated. During 1990-1993, the mean number of milliliters used by each hospital annually (based on 9-15 hospitals each year) increased from 10 mL to 203 mL (Table_2). Because most hospitals also do not monitor the characteristics (e.g., age and weight) of persons who receive rabies PEP, the average volume of HRIG administered to each patient was estimated to be 8 mL -- a dosage appropriate for a 132-lb person. To estimate the total number of doses of HRIG administered, the mean number of milliliters dispensed was divided by 8 mL. Based on these data, the estimated number of persons treated at Connecticut hospitals increased from 41 in 1990 to 887 during the first 9 months of 1994 (Table_2).

Complete sales data for HRIG sold in Connecticut were available from both manufacturers only for 1993. HRIG sufficient for an estimated 1879 doses (based on an 8-mL dose per patient) was sold to Connecticut health-care providers. Based on these data, in 1993, PEP was administered to 1879 persons in Connecticut.

Reported by: RS Nelson, DVM, GH Cooper, Jr, ML Cartter, MD, JL Hadler, MD, State Epidemiologist, Connecticut Dept of Public Health. Viral and Rickettsial Zoonoses Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Since the 1950s, cases of human rabies in the United States have steadily declined. During 1980-1995, only 18 indigenously acquired cases occurred, and no human deaths were attributed to the raccoon rabies virus variant associated with the epizootic (1-3). In Connecticut, a bat-associated case in 1995 was the first human case to be reported since 1932 (4). The decline in human rabies cases, in part, reflects the availability of an effective treatment for humans following exposure to a rabid animal and widespread use of canine rabies vaccination. The Advisory Committee on Immunization Practices (ACIP) periodically revises recommendations to guide decisions regarding treatment following exposure (5). Adherence to these guidelines should reduce the number of unnecessary administrations of PEP, associated costs, and potential risks for adverse reactions.

The findings in this report are subject to at least three limitations. First, because data from the hospital pharmacies for 1990-1993 were incomplete, the findings for those years may not be respresentative of all hospital pharmacies in Connecticut. Second, the amount of HRIG dispensed by hospital pharmacies was used as a surrogate measure of the number of treatments administered and does not account for unused HRIG; therefore, these findings may overestimate the number of persons receiving rabies PEP in Connecticut. Third, because of the use of an estimate for the average bodyweight of persons receiving rabies PEP in Connecticut, the estimate of PEP usage may not be precise.

Despite limitations in the precision of the estimates of the number of administrations of rabies PEP in Connecticut, estimates such as those presented in this report are one important measure of the cost associated with rabies prevention. PEP usage also may reflect changes in the epizootiology of rabies in specific areas, as illustrated by the increased numbers of persons who received PEP in areas affected by raccoon rabies (6).

The findings in this report indicate an increasing trend in the administration of rabies PEP that corresponded with the statewide spread of racoon rabies in Connecticut. Similarly, administration of PEP increased in two counties in New Jersey during 1988-1990 and in New York state during 1992-1993 as the raccoon rabies epizootic progressed in those states (6,7).

One of the national health objectives for the year 2000 is to reduce the number of rabies PEP administrations in the United States to no more than 9000 per year (objective 20.12) (8). Although national PEP usage has not been estimated since 1980-1981, the findings in Connecticut and other states (6,7) suggest this objective is unlikely to be achieved.

References

1. CDC. Human rabies -- West Virginia, 1994. MMWR 1995;44:86-7,93.

2. CDC. Human rabies -- Washington, 1995. MMWR 1995;44:625-7.

3. Connecticut Department of Public Health. Human rabies case -- Connecticut. Connecticut Epidemiologist 1995;15:21-2.

4. CDC. Human rabies -- Connecticut, 1995. MMWR 1996;45:207-9.

5. CDC. Rabies prevention -- United States, 1991: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1991;40(no. RR-3).

6. CDC. Raccoon rabies epizootic -- United States, 1993. MMWR 1994;43:269-73.

7. Uhaa IJ, Dato VM, Sorhage FE, et al. Benefits and costs of using an orally absorbed vaccine to control rabies in raccoons. JAVMA 1992;201:1873-82.

8. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991:122;DHHS publication no. (PHS)91-50213.

• For 1994, data were reported for January-September.

TABLE 1. Hospital charges for human rabies immunoglobulin (HRIG), rabies
vaccine, and postexposure prophylaxis * (PEP), by product -- Connecticut,
1994
===========================================================================

                       No. hospitals      Hospital charge to patient
                         reporting        --------------------------
Product                    (n-32)           Median       (Range)
---------------------------------------------------------------------------
Rabies vaccine               19             $ 189     ($ 80-$ 594)

HRIG
  2 mL                       17             $ 136     ($ 67-$ 400)
 10 mL                       17             $ 504     ($268-$1577)

PET
 For persons
  weighing 33 lbs +          14             $1127     ($481-$3371)
 For persons
  weighing 132 lbs &         16             $1430     ($709-$4233)
 For persons
  weighing 165 lbs @         16             $1498     ($787-$4548)
---------------------------------------------------------------------------
* PEP consists of doses of rabies vaccine and HRIG based on the patient's
  weight.
+ 2 mL HRIG and five vaccine doses.
& 8 mL HRIG and five vaccine doses.
@ 10 mL HRIG and five vaccine doses.
===========================================================================

TABLE 2. Number of milliliters of human rabies immunoglobulin (HRIG) dispensed
at hospitals and estimated total doses administered, * by year -- Connecticut,
1990-1994 +
==================================================================================
            No. hospitals     HRIG dispensed     Total HRIG    Estimated
              reporting     per hospital (mL)     dispensed      total
Year            (n=32)       Mean     (Range)       (mL)         doses
----------------------------------------------------------------------------------
1990               9           10    ( 0- 36)         90           41
1991               9           63    ( 0-343)        565          260
1992              11          163    (12-470)       1790          672
1993              15          203    (10-490)       3050          837
1994 +            28          215    (26-548)       6016          887
----------------------------------------------------------------------------------
* Because most hospitals do not monitor the characteristics (e.g., age and weight)
  of persons who receive rabies postexposure prophylaxis, the average volume of
  HRIG administered to each patient was estimated to be 8 mL--a dosage appropriate
  for a 132-pound person. To estimate the total number of doses of HRIG
  administered, the mean number of milliliters dispensed was divided by 8 mL.
+ Because most hospital pharmacies do not monitor the number of patients who
  receive rabies postexposure prophylaxis, the amount of HRIG dispensed by the
  hospital pharmacies was used as a surrogate measure of the number of treatments
  initiated.
& Reported for January-September.
==================================================================================

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