The role of child care in a community-wide outbreak of hepatitis A

Objective. To evaluate the role of child care centers in a community-wide h epatitis A epidemic. Methods. We analyzed surveillance data during an epidemic in Maricopa Count y, Arizona, from January to October 1997 and conducted a case-control study using a sample of cases reported from June to November. Cases were physici an-diagnosed and laboratory confirmed; control subjects were frequency matc hed by age and neighborhood. Information regarding hepatitis A risk factors , including child care-related exposures, was collected. Characteristics of all licensed child care centers in the county were obtained through review of computerized lists from the Arizona Office of Child Day Care Licensing. Surveillance data were linked to the child care list to determine which ce nters had reported hepatitis A cases. We conducted univariate and multivari ate conditional logistic analyses and calculated population attributable ri sks (PAR). Results. In total, 1242 cases (50/100 000 population) were reported. The hi ghest rates occurred among people aged 0 to 4 (76/100 000), 5 to 14 (95/100 000), and 15 to 29 (79/100 000) years. The most frequently reported risk f actor was contact with a hepatitis A patient (45%). However, nearly 80% of these contacts were with individuals who attended or worked in a child care center. Overall, child care center-related contact could have been the sou rce of infection for 34% of case-patients. In the case-control study, case- patients (n = 116) and control subjects (n = 116) did not differ with respe ct to demographic characteristics. A total of 51% of case-patients compared with 18% of control subjects reported attending or working in a child care setting (direct contact; adjusted odds ratio [OR]: 6.0; 95% confidence int erval [CI]: 2.1-23.0) or being a household contact of such a person (indire ct contact; OR: 3.0; 95% CI: 1.3-8.0). In age-stratified analyses, the asso ciation between hepatitis A and direct or indirect contact with child care settings was strongest for children <6 years old and adults aged 18 to 34 y ears. Household contact with a person with hepatitis A also was associated with hepatitis A (OR: 9.2; 95% CI: 2.6-58.2). The presence of a child <5 ye ars old in the household was not associated with hepatitis A. The estimated PAR for direct child care contact was 23% (95% CI: 16-34), for indirect ch ild care contact was 21% (95% CI: 13-35), and for any child care contact wa s 40% (95% CI: 30-53). Information on 1243 licensed child care centers was obtained, with capacity ranging from 5 to 479 slots (mean: 87). Thirty-four (2.7%) centers reported hepatitis A cases. Centers that had a mean capacit y of >50 children were more than twice as likely to have had a reported cas e of hepatitis A (OR: 2.6; 95% CI: 1.1-6.7). Among the 747 centers that acc epted >50 children, having infant (OR: 3.7; 95% CI: 1.6-8.3), toddler (OR: 6.3; 95% CI: 2.2-20.0), or full-day service (OR; undefined; 95% CI: 1.7-pro portional to) was associated with having a reported case of hepatitis A. Conclusions. In Maricopa County, people associated with child care settings are at increased risk of hepatitis A, and child care attendees may be an a ppropriate target group for hepatitis A vaccination. Considering the estima ted proportion of children who attended child care and were old enough to r eceive hepatitis A vaccine (greater than or equal to2 years of age) and the calculated PAR, approximately 40% of cases might have been prevented if ch ild care center attendees and staff had been vaccinated. However, epidemiol ogic studies indicate that the proportion of cases that are attributable to child care center exposure varies considerably among counties, suggesting that this exposure may be associated with an increased risk of hepatitis A in some communities but not in others. To prevent and control hepatitis A e pidemics in communities, the Advisory Committee on Immunization Practices a nd the American Academy of Pediatrics have adopted a longterm strategy of r outine vaccination of children who live in areas with consistently elevated hepatitis A rates. After demonstrating cost-effectiveness, a rule was impl emented in January 1999 to require hepatitis A vaccination of all children who are aged 2 to 5 years and enrolled in a licensed child care facility in Maricopa County. Other communities with similar epidemiologic features mig ht consider routine vaccination of child care center attendees as a long-te rm hepatitis A prevention strategy. Consistent with current recommendations , in communities with persistently elevated hepatitis A rates where child c are center attendance does not play an important role in hepatitis A virus transmission in the community, child care centers may nonetheless provide a convenient access point for delivering hepatitis A as well as other routin e childhood vaccinations.