Severe complications associated with varicella: Province of Quebec,April 1994 to March 1996

OBJECTIVE:

To determine the frequency and severity of serious complications associated with varicella in Quebec; the frequency and severity of cases of congenital varicella; and hospital costs associated with hospitalizations for varicella.

STUDY DESIGN:

All hospitalizations related to varicella were identified through the use of a hospital data bank and pertinent data were collected from hospital records.

SETTING:

Province of Quebec with a population of 6,895,960 people.

STUDY POPULATION:

All cases with a principal or secondary diagnosis of varicella hospitalized in Quebec between April 1, 1994 and March 31, 1996.

OUTCOME MEASURES:

Types of complications and reason for hospitalization, risk of complications and calculation of associated costs were studied.

RESULTS:

Nine hundred nine eligible hospitalizations were identified between April 1, 1994 and March 31, 1996. In all, 583 (64.1%) hospitalizations were for the treatment of complications, 127 (14.0%) for administration of intravenous acyclovir and 199 (21.9%) for supportive care. Healthy people accounted for 644 (70.8%) hospitalizations and immunosuppressed individuals for 136 (15.0%). Among children, one-half of the principal complications were skin infections, while 13.5% and 8.4% of principal complications were pneumonia and neurological complications, respectively. Among adults, the most common complication was pneumonia, with a rate of 43.5%, followed by thrombocytopenia and skin infections, with rates of 22.2% and 14.8%, respectively. The complication rate was 29.2 cases/10,000 cases of varicella.

CONCLUSIONS:

Although perceived as a benign childhood disease by the general population, varicella may be accompanied by severe complications. Morbidity associated with varicella is one of the elements that must be considered when evaluating the usefulness of varicella vaccine.Key Words: Communicable diseases control, Disease notification, Population surveillance, Public health, VaricellaVaricella is usually a benign disease in children. More severe forms of the disease and complications occur proportionately more frequently among adolescents, adults and immunosuppressed people (1-3). In the United States, the average annual number of hospitalizations for varicella has been estimated at 3837, 70% of which were among children under the age of 10 years (1). The risk of hospitalization increases with age: 42 and 127 hospitalizations/10,000 cases were reported for 15- to 19-year olds and for adults 20 years old and over, respectively, compared with about 10 hospitalizations/10,000 for children aged 14 years and younger (1).According to an American study of 4884 cases of varicella carried out over two years in the early 1990s, 100 presented at least one complication, for a rate of 205 cases with complications/10,000 cases of varicella, and 30 had to be hospitalized (hospitalization rate 61/10,000) (2).Among people 19 years of age or younger, skin and soft tissue infections were predominant, and were the cause of over 50% of hospitalizations; among adults, varicella pneumonia was the most common complication. Among both groups, encephalitis, dehydration and hepatitis were among the other, less common causes of hospitalization (2).In Canada, the Canadian Medical Association Journal (4) noted a rate of 2.3 hospitalizations/100,000 in 1984, with hospitalization rates of 27.5/100,000 among infants younger than one year of age, 17.5/100,000 among one- to four-year olds and 5.5/100,000 among five- to 14-year olds (4). In a university-affiliated paediatric hospital in Calgary, Alberta, serving a population of 1.2 million and with approximately 6500 admissions/year, 165 children were hospitalized for varicella (2.6 cases of varicella/1000 admissions) between January 1, 1983 and December 31, 1992 (5).In the present study, we evaluated the morbidity associated with varicella using hospitalized cases and costs related to these hospitalizations.