Abstract
Objective. The purpose of this study was to assess the direct medical costs and productivity losses associated with uncomplicated chickenpox (no hospitalization) in Canada.
Methods. A total of 179 otherwise healthy 1- to 9-year-old children with active chickenpox were recruited from schools, day care centers, and physician offices in 5 provinces. Direct medical (physician contacts, medication, and diagnostic tests) and nonmedical (personal expenses including child care) resources expended during the illness were determined by caregiver interview. Productivity losses attributable to the disease were determined by assessing caregiver time lost from work and daily activities. Unit costs for all resources were obtained from sources in 2 provinces, and per-patient treatment costs were determined from the patient, Ministry of Health, and societal perspectives.
Results. From a societal perspective, the per-case cost for children from 1 to 4 years of age and from 5 to 9 years of age was $370.2 and $236.5, respectively. Direct medical costs accounted for 10% of the total costs in both groups. The largest cost driver in patient care was caregiver productivity losses, which amounted to $316.5 in the younger age group and to $182.7 in the older age group. Based on an estimated yearly incidence of 344 656 cases of uncomplicated chickenpox in Canada, the total annual societal burden of the disease can be estimated at $109.2 million, with a cost to the Ministry of Health of $11.2 million.
Conclusion. Chickenpox is one of the last common childhood diseases prevalent in Canada, and the uncomplicated disease, despite its rather benign course, imparts a large annual economic burden.
Chickenpox, or varicella, is the primary infection caused by the varicella-zoster virus.1 The disease is highly contagious, occurs most frequently in childhood, and usually follows an uncomplicated course in otherwise healthy children. It is generally accepted that the yearly incidence of chickenpox approximates the birth cohort,2–4 which for Canada translates into ∼344 000 cases per year (95% of birth cohort).5Published age-specific incidence rates for the disease show considerable variation. The most recent epidemiologic study conducted in Canada (1986),6 using limited provincial data, indicates that children 5 to 9 years of age had the highest incidence rate (∼21 cases per 1000 population) and that children younger than age 15 years accounted for 96% of the total cases reported. Five- to 9-year-olds also had the highest incidence in studies conducted in the United States between 1980 and 1990 (91.1 cases per 1000 children)7 and between 1990 to 1992 (105 cases per 1000 children).8 However, in a more recent population-based study conducted in 1995, the incidence rate for this age group (86 cases per 1000 children) was 44% lower than the rate for 1- to 5-year-old children, suggesting that the rate of varicella infection is increasing in preschool children.9
For the majority of children with chickenpox, the disease is mild to moderate, and management focuses on symptom relief and treatment of minor complications, primarily secondary skin infections. Acyclovir can shorten the course of illness,1 ,2 but the clinical and economic benefits of routine therapy for otherwise healthy children are unclear.2 ,10 Healthy children infrequently develop serious complications including sepsis, focal infec7tions such as osteomyelitis or septic arthritis, pneumonia, or encephalitis, or death.11 ,12
The economic burden of chickenpox is significant. Lieu and colleagues13 calculated that with an annual birth cohort of ∼4 million in the United States, total societal costs associated with the disease in otherwise healthy children would be $529 million per year ($US 1990). The bulk of this cost (83%) was attributable to days lost from work by caregivers, and it is this cost that drives the overall economic impact of the disease. Similar values and conclusions with regards to the impact of productivity costs have been determined in other studies.14 In addition to the economic impact, the disease also has an effect on the quality of life of caregivers15 and patients.
There currently are no data available describing the economic burden of chickenpox in Canada. The objective of this study was to assess the cost of chickenpox in Canada by separating the disease into two components: the common uncomplicated disease and the complicated disease requiring hospitalization. The costs associated with uncomplicated chickenpox are the subject of this report. The cost of complicated chickenpox together with the overall costs attributable to both uncomplicated and complicated cases of chickenpox in Canada are presented in a companion paper.16
METHODS
Study Design
This study was designed to quantify prospectively the direct medical, nonmedical, and productivity costs associated with the care of uncomplicated (not requiring hospitalization) childhood chickenpox in Canada. Patients were recruited from day care centers, schools, and physician offices across Canada over two 3-month periods from April to June and from September to November 1997. The recruitment of children and data collection were coordinated by investigators at eight Canadian pediatric centers. Patients were identified by day care coordinators, school officials, or clinic nurses, or through advertisements, and were recruited at each site by a nurse who contacted the parents or legal guardians inviting them to participate in the study. Eligibility criteria for inclusion in the study were children between 1 and 9 years of age, absence of a major chronic illness, and active chickenpox defined as presence of the characteristic rash. Subjects were excluded if they were admitted to hospital during the study period. The study protocol received ethical approval from the appropriate committee at all participating institutions, and informed consent was obtained from the legal guardian(s) of all participants.
Data Collection
Data were collected through two telephone interviews with the parents or legal guardians. The first took place at the time the child was recruited, and the second approximately 3 weeks after the child had recovered from the disease. The interview was conducted by the nurse at each site using a standard questionnaire designed to collect sociodemographic, clinical, and resource utilization data.
Sociodemographic information was determined for both the child and his or her caregivers. Caregivers were defined as the birth parents, legal guardians, or live-in partners who resided in the same house with the child full-time. Clinical data collected included the person who made the first diagnosis of chickenpox, presence or absence of a confirmatory diagnosis by a health professional, and the duration of the rash. Resource utilization data collected over the course of the child's infection included direct medical and nonmedical resources utilized by the patients or their families. Specifically, these included the number of physician or nurse contacts (including office visits, home visits and telephone calls); diagnostic tests and procedures; and prescription drugs and the personal expenses incurred by the family (eg, child care, transportation, nonprescription drugs, etc). Additional resources collected were the number of days missed from school or day care by the child; the number of days missed from work by the caregivers or any other employed family member who may have participated in the care of the child; and the time lost by the caregivers from normal daily leisure activities. For days missed from school or day care, the caregiver also was asked to indicate how many days were missed solely as a result of mandated exclusion from attendance during the contagious period of the rash (ie, a situation in which the caregiver thought the child could have returned to school but was prevented from doing so by the exclusion rule). Caregivers also were asked how their own well-being (eg, sleep, anxiety) was affected during the course of the child's illness.
Cost Association and Structure
Cost valuation for the utilized resources was performed from the patient, Ministry of Health, and societal perspectives. The patient perspective included costs that were borne by the family including personal expenses (nonmedical) and time lost from work and daily activities by the caregivers (productivity costs). Any direct medical costs, including medical contacts and prescription medications, were considered under the Ministry of Health perspective. The societal perspective included all direct medical, nonmedical, and productivity costs. All costs are expressed in 1997/1998 Canadian dollars. Cost data for direct medical resources was obtained from Ontario and Quebec provincial reimbursement schedules and presented as an average value. These average cost values were used as an estimate for all medical resources in Canada. For direct nonmedical resources, costs were obtained directly from the child's caregivers. The cost of days missed from work and time lost was estimated by applying the average daily income for the geographic region, based on postal code data defining where the caregiver resided.
The average cost per patient was calculated from the three perspectives for day care and school-age children. The annual total cost of uncomplicated cases of chickenpox was calculated using an estimated incidence rate for uncomplicated cases in Canada. This was determined by assuming 95% of the estimated annual birth cohort has chickenpox each year, less the number of cases that are hospitalized because of complications.4 It also was assumed for the analysis that day care age children represent 60% of all chickenpox cases and school age children represent the remaining 40%.9 In addition, within the day care age group, the average per-patient cost was weighted to reflect the number of children in this age group who actually attend day care. Current estimates are that 46% of children between 18 months and 6 years of age attend regulated day care in Canada.17
Sensitivity Analysis
Three sensitivity analyses were performed to determine the impact of variations on key parameters on overall costs. In the first analysis, the cost of days missed from work by active caregivers was varied by ±20%. For the second analysis, the cost applied to time lost by the caregivers was the minimum wage in Canada instead of the average income from their geographic region. Finally, the average per-patient cost of day care age children was calculated assuming that 60% of children in this category actually attend day care in Canada.
RESULTS
A total of 179 patients from 5 provinces were recruited for the study in the 6-month period (Table 1). Of these cases, 92 were of day care age (1–4 years), and 87 children were of school age (5 to 9 years). Of the former population, 75 of these children (82%) were actually attending day care and, of these, 50 were recruited through a day care network in the Toronto region. The general sociodemographic data for all the patients and their caregivers are presented in Table 2.
Patient Population Distribution and Recruitment of Uncomplicated Cases of Chickenpox
Patient and Caregiver Sociodemographics of Uncomplicated Cases of Chickenpox
Using the parent interview, resource utilization patterns were established for infected children in each age group (Table 3). There were few direct medical resources reported by the caregivers, although >50% of the children who attended day care had a physician visit. A total of 46% of all cases recruited had their diagnosis of chickenpox confirmed by a physician. For children 1 to 4 years of age attending day care, the average number of days missed from day care was 5.6. For the school children, an average of 4.2 days of school were missed because of chickenpox. In addition, 18% of the caregivers of school children reported that a portion of school days missed by their child was attributable to an exclusion rule accounting for an average of 3.0 days per child. Corresponding figures for day care age children were 19% of children missing an average of 3.2 days because of the exclusion rule (Table 3).
Resource Utilization for Uncomplicated Cases of Chickenpox
To assess the wider impact of the disease, days lost from work and time lost from daily activities were assessed for all caregivers and other household members living permanently with the child (Table 3). Of the children who attended day care, 84% and 92% of the primary and secondary caregivers were employed, either part-time or full-time, respectively, and during the course of the disease, these individuals missed a combined total of 3.4 days from work. For the same group, the additional total number of hours lost from daily activities was 13.3 hours. In contrast, for those children not attending day care, 35% and 87% of the primary and secondary caregivers were employed, respectively, and they missed a combined total of only 0.5 days from work but did report a loss of 18.3 hours from daily activities. In the school age group, the average time missed from work for employed caregivers was 1.6 days (total for caregivers 1 and 2).
By attaching unit costs to the days missed from work and time lost, the total average productivity cost for day care age children attending day care was $343.3 per patient and $198.3 for children of the same age but not in day care, a 73% higher cost for the former group (Table 4). In the school-age group, the average productivity cost was $182.7, with 41% of this cost allocated to days missed from work by the caregivers. The average direct medical cost per patient was similar for all three groups of patients, with medical contacts representing >90% of the total cost (Table 4).
Costs Associated With Uncomplicated Cases of Chickenpox
The total average per-patient cost from the patient, Ministry of Health, and society perspectives is summarized in Table 5. From the patient perspective, the total average cost per patient varied from $333.6 to $211.1 in the day care age and school age group. This cost included all direct nonmedical resources, days missed from work, and time lost from daily activities for the caregivers. The average per-patient cost for the day care age group was based on the assumption that 46% of children attend day care. From the societal perspective, the average per-patient cost was $370.2 in the day care age group and $236.5 in the school age group. The costs from the patient perspective accounted for the majority of the societal cost in both age groups. The overall yearly cost of treatment of 344 656 uncomplicated chickenpox cases in Canada was found to be $11.2 million from the Ministry of Health perspective, representing 10% of the overall societal cost of $109.2 million.
Per Patient Costs of Uncomplicated Cases of Chickenpox
For the sensitivity analysis, when the cost of days missed from work was varied by ± 20%, the overall total cost to society changed by 6.5% (Table 6). When the minimum wage was used to estimate the cost of time lost from daily activities rather than the average income from the caregiver's geographic region, the overall cost to society decreased by 12.8%. In a final sensitivity analysis, the per-patient costs for the day care age children were recalculated to reflect a situation in which 60% of this population attended day care. Under these conditions, the per-patient cost increased to $399.7 and the total economic impact of uncomplicated chickenpox increased by $6.1 million.
Sensitivity Analysis on the Per-patient Cost of Uncomplicated Cases of Chickenpox
DISCUSSION
The design and recruitment strategy used in the present study permitted a detailed analysis of the two age groups (1–4 year-olds and 5–9 year-olds) that represent close to 80% of the yearly cases of varicella.4 ,7 In addition, the families recruited were representative of the Canadian population in terms of caregiver employment status and ethnic diversity.18 The primary sources of data for this study were parent interviews, and for the majority of patients recruited a caregiver also provided the diagnosis of chickenpox. In half of these cases, a physician confirmed the diagnosis. Previous studies have shown that in this situation, parents are 90% to 100% accurate in their diagnosis.19
The per-patient direct medical costs of uncomplicated chickenpox was estimated at $36.6 and $26.2 for day care age and school children, respectively. Because there was negligible prescription use and few tests and procedures reported, this direct cost was almost entirely attributable to medical contacts. Previous US studies also have reported that prescriptions have only a minor impact on the overall cost of the disease and that only 10%9 to 12%19 of chickenpox patients have been reported to use prescription medications.
The overall number of consultations, which averaged one per child, was similar to those reported in a 1983 Los Angeles study20 but higher than the 15% rate reported in a more recent Rochester, Minnesota, study.9 However, in the latter study, of the total cases recruited (911), 364 were secondary cases, which may have lowered the overall percentage requesting health care. In a third US study, Lieu and colleagues19 reported that approximately one third of young children up to 6 years of age with chickenpox had a medical consultation.
The average per-patient productivity costs were $316.5 for day care age children and $182.7 for school children, based primarily on a total of 39 and 1.6 days lost from work by caregivers for both groups, respectively. These figures are comparable with those from other published studies.9 The present study also indicates that the productivity costs associated with young children who attend day care are 73.1% higher than costs associated with children not in day care. This suggests that for working parents with children in day care, the economic impact of the disease is considerably higher than it is for other groups. On a national basis, this may result in a significant economic impact because substantial numbers of children attend day care in Canada. A review of child care arrangements for 1995 and 1996 reports that 14% of children 18 to 36 months of age and 32% 3 to 6 years of age attend regulated center-based day care.17These numbers are higher when nonregulated day care and alternative arrangements for child care are included. In addition, the parental impact of the disease is also higher in this group because, based on the data accumulated in the present study, the average amount spent by these parents on alternate care arrangements was $18.4 per patient, whereas the parents of children not in day care spent $2.9.
In the present study, the average number of days missed from day care or school was 5.6 and 4.2, respectively. These missed days correlate well with the number of work days lost by caregivers for the day care age group. However, in US studies, the number of days missed from school or day care are higher, and values of 7.6 and 5.6 days, respectively, have been reported by Lieu and colleagues.19However, only 1.6 days of work per case were missed by the parents. In the same study, parents reported that school children needed to stay home for an average of 4.3 days because of the exclusion rule. The variation in exclusion policies may be one reason for the discrepancies between days missed from day care or school in the two studies. To estimate the impact of the exclusion rule policy in Canada, caregivers were asked whether their child lost day care or school days solely because of such a rule. The average number of days the child was kept at home because of the exclusion rule alone was 0.6 days for both groups, meaning that the parents would keep their children at home for at least 5.0 days and 3.6 days, even in the absence of an exclusion rule.
The total per-patient cost for uncomplicated chickenpox from a society perspective was $370.2 for day care age children and $236.5 for school children. The major cost driver in both groups was the productivity cost of days lost from work and time lost by caregivers, which contributed, on average, 70% to the per-patient cost of the disease. Although the per-patient costs are low, because the yearly incidence of chickenpox is high (estimated at 344 656 cases per year in Canada), the disease has a substantial national economic impact, with a yearly societal cost estimated at $109.2 million.
One of the limitations of the present study is that the overall economic impact of uncomplicated cases was estimated using the treatment costs of children 1 to 9 years of age. Although most cases of uncomplicated chickenpox occur in this age group (80%),7costs for children younger than 1 and older than 9 years of age were not assessed. Per-patient costs for these children may be higher than for the group assessed in the present study because of increased rates of physician consultations in infants and higher complication rates in children older than age 10. A second limitation is in the recruitment of day care age children. Eighty percent of the children recruited were attending day care, and this may have resulted in an overestimation of per-patient costs for this group. However, in the calculation of the total per-patient cost of a day care age child, it was assumed that only 46% of these children attend day care, to reflect regulated day care attendance rates in Canada. In addition, in a sensitivity analysis, the numbers again were adjusted to reflect a 60% day care attendance to account for children who attend unregulated day care, and the overall cost of uncomplicated chickenpox increased under these conditions.
Few previous studies have assessed the cost of uncomplicated chickenpox as an isolated disease not associated with the short-term and long-term costs of complications. However, in a 1991–1992 study, Lieu and colleagues estimated the cost of the disease, in the absence of hospitalization, at $US 313 per family, similar to the values determined here and in a 1995 modeling study, Paul and associates15 calculated a per-patient cost of $US 454.2 for uncomplicated chickenpox. The latter study included a component for the restriction of usual activities similar to the measurement of time lost in the present study. Time lost provides a means of assessing the broader impact of the disease and, as used in the present study, quantifies the time lost by applying a monetary value.21
Chickenpox also has a broader impact in terms of the quality of life of the child and caregiver during the course of the disease. There have been no specific studies of the quality of life in chickenpox, although Paul and co-workers15 incorporated a quality of life component into their varicella cost-consequences model, based on assumptions on the impact of the disease. They defined this impact in terms of caregiver distress days, which paralleled the duration of the symptoms, resulting in a 20% reduction in quality of life. The pilot assessment of caregiver well-being in the present study confirms that the disease has a substantial impact on the caregivers. Forty percent of the caregivers indicated that their sleep was moderately effected, whereas 25% reported a severe effect on sleep. Greater than 50% of all caregivers reported a moderate or severe effect on their social/recreational time.
Chickenpox is one of the last common communicable childhood diseases still prevalent in Canada. The present study demonstrates that because of the high incidence of the disease, uncomplicated chickenpox has a considerable economic impact on Canadian society. A decrease in the quality of life of caregivers and patients also supports that the disease has broader implications that go beyond economic parameters. As shown in the companion article in this issue, the economic impact is enhanced when the costs of hospitalization resulting from the disease are incorporated.
ACKNOWLEDGMENTS
This study was funded by Merck Frosst Canada.
We thank the study nurses who helped make this work possible: Ardith Ambrose, Johanne Bonneau, Helen Etherington, Cory Kress, Lisa Palmerino, Lorraine Piché-Walker, Ann Roth; and Irene Dehem for her assistance with the analysis.
Footnotes
- Received September 14, 1998.
- Accepted November 30, 1998.
Reprint requests to (C.F.) Quintiles Canada, 100 Alexis-Nihon, Suite 800, Ville St-Laurent, Québec H4 M 2P4. E-mail:cfitzsim{at}qmtl.quintiles.com
REFERENCES
- Copyright © 1999 American Academy of Pediatrics
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