Biomedical subjects
T A Lieu
Publications and source records attributed to T A Lieu.
Neonatal group B streptococcal infection in a managed care population. Perinatal Group B Streptococcal Infection Study Group.
OBJECTIVE: In a health maintenance organization population, we determined the incidence of early-onset (at less than or equal to 7 days) neonatal group B streptococcal (GBS) disease, the sensitivity and prevalence of labor risk factors, the adherence to a protocol for intrapartum antibiotics, and the costs for care of and outcomes of affected infants. METHODS: Mothers and infants at four health maintenance organization hospitals in northern California in 1989 to 1995 were studied retrospectively using computerized databases and chart review. In 1994, two of the four hospitals had adopted protocols similar to the ACOG recommendations for intrapartum antibiotics for women with labor risk factors (preterm, temperature 100.4F or higher, or rupture of membranes (ROM) 18 hours or more). RESULTS: Among the 79,940 live births, the incidence of early-onset neonatal GBS infection was higher among preterm than among term infants (3.1 compared with 0.9 per 1000). Before protocol adoption, 68% of 65 infants with GBS had mothers with labor risk factors. Approximately 18% of all mothers had labor risk factors: 7.7% had preterm delivery, and 10.6% had term delivery with fever and/or ROM 18 hours or more. At the two hospitals that adopted GBS protocols, GBS incidence was reduced from 1.3 per 1000 in the preprotocol period to 0.8 per 1000 in the postprotocol period (P=.08). Six cases of neonatal GBS occurred after protocol adoption. Of these, four were not preventable under the protocol and two might have been preventable if protocol had been followed. Three of the 19 preterm infants with group B streptococcal disease died. CONCLUSION: Risk factor-based protocols hold some promise to reduce GBS disease, but clinical strategies to promote protocol adherence are needed.
Varicella serology among school age children with a negative or uncertain history of chickenpox.
BACKGROUND: Clinicians who offer varicella vaccination to school age children face the dilemma of whether to serotest or vaccinate presumptively. Varicella seroprevalence among 7- to 12-year-old children with negative or uncertain histories has not previously been studied. Our main objective was to describe varicella seroprevalence among children ages 7 to 12 years with a negative or uncertain history of chickenpox. METHODS: This was a cross-sectional study of children whose clinicians had ordered varicella serotesting. Guidelines from the medical group's regional pediatric infectious disease specialists recommended obtaining varicella serology on all children 7 to 12 years old with a negative or uncertain history. Parents were interviewed by telephone about the child's history of chickenpox before test results were completed. RESULTS: Varicella seroprevalence ranged from 9% among 7-year-olds whose parents said they had definitely not had chickenpox to 68% among 11-year-olds whose parents were not sure whether they had had chickenpox. Among children whose parents were uncertain about their chickenpox history, almost one-half (48%) were seropositive. Twenty-five percent of children whose parents said they definitely had not and 32% of children whose parents said they had probably not had chickenpox were seropositive. Of parents whose children had experienced serotesting, 73% said they would prefer to have the blood test first rather than presumptive vaccination. For a large health maintenance organization, it was projected to be most cost-effective (in terms of cost per chickenpox case prevented) to recommend testing for children 9 to 12 years old with uncertain histories of chickenpox. CONCLUSIONS: We conclude that among children 7 to 12 years old with negative or uncertain histories of chickenpox, varicella seroprevalence ranges from 9 to 68% depending on age and clinical history. Parents are generally receptive to serotesting, although individual preferences vary. In the population we studied it would be most cost-effective to recommend testing before deciding about vaccination for children 9 to 12 years old with uncertain histories of chickenpox.
Computer-based models to identify high-risk children with asthma.
Effective management of populations with asthma requires methods for identifying patients at high risk for adverse outcomes. The aim of this study was to develop and validate prediction models that used computerized utilization data from a large health-maintenance organization (HMO) to predict asthma-related hospitalization and emergency department (ED) visits. In this retrospective cohort design with split-sample validation, variables from the baseline year were used to predict asthma-related adverse outcomes during the follow-up year for 16,520 children with asthma-related utilization. In proportional-hazard models, having filled an oral steroid prescription (relative risk [RR]: 1.9; 95% confidence interval [CI]: 1.3 to 2.8) or having been hospitalized (RR: 1.7; 95% CI: 1.1 to 2.7) during the prior 6 mo, and not having a personal physician listed on the computer (RR: 1.6; 95% CI: 1.1 to 2.3) were associated with increased risk of future hospitalization. Classification trees identified previous hospitalization and ED visits, six or more beta-agonist inhalers (units) during the prior 6 mo, and three or more physicians prescribing asthma medications during the prior 6 mo as predictors. The classification trees performed similarly to proportional-hazards models, and identified patients who had a threefold greater risk of hospitalization and a twofold greater risk of ED visits than the average patient. We conclude that computer-based prediction models can identify children at high risk for adverse asthma outcomes, and may be useful in population-based efforts to improve asthma management.
Effectiveness and cost-effectiveness of letters, automated telephone messages, or both for underimmunized children in a health maintenance organization.
BACKGROUND: Immunization rates have improved in the United States, but are still far from the national 90% goal for the year 2000. There is scant evidence about the effectiveness and costs of automated telephone messages to improve immunization rates among privately insured children. OBJECTIVE: To evaluate the effectiveness and cost-effectiveness of sending letters, automated telephone messages, or both to families of underimmunized 20-month-olds in a health maintenance organization (HMO). METHODS: In this randomized trial, underimmunized 20-month-olds identified by the HMO's computerized immunization tracking system were assigned to one of four interventions: 1) an automated telephone message alone; 2) a letter alone; 3) an automated telephone message followed by a letter 1 week later; and 4) a letter followed by an automated telephone message 1 week later. The primary outcome was receipt of any needed immunization by 24 months of age. Decision analysis was used to evaluate the projected cost-effectiveness of the alternative strategies. RESULTS: A total of 648 children were randomized. A letter followed by a telephone message (58% immunized) was significantly better than either a letter alone (44% immunized) or a telephone message alone (44% immunized). A telephone message followed by a letter (53% immunized) also was more effective than either alone, although the differences were not statistically significant. Among a similar comparison group that received no systematic intervention, 36% were immunized. The estimated cost per child immunized was $7.00 using letters followed by automated telephone messages, $9.80 using automated telephone messages alone, and $10.50 using letters alone. Under alternative cost assumptions for automated telephone messages and mailed messages, the cost per child immunized ranged from $2.20 to $6.50. CONCLUSIONS: For underimmunized 20-month-olds in this HMO setting, letters followed by automated telephone messages were more effective and cost-effective than either message alone. The cost-effectiveness of automated telephone messages and letters may vary widely depending on the setting, and choices among strategies should be tailored to the populations being served.
Parent reports on willingness to accept childhood immunizations during urgent care visits.
OBJECTIVES: To 1) describe whether parents would be willing to accept childhood immunizations at urgent care visits; and 2) identify predictors of parents' willingness to accept childhood immunizations at urgent care visits. DESIGN AND PARTICIPANTS: Cross-sectional telephone survey of parents of children aged 18 to 24 months who were underimmunized according to a computerized immunization tracking system and who had recently made an urgent care visit in a regional group-model health maintenance organization in Northern California. Chart review was conducted to confirm immunization status and to identify contraindications to vaccination. RESULTS: Of the 424 eligible participants, 351 (83%) completed interviews. Children with contraindications to vaccination and children who were actually up-to-date at the time of the urgent care visit were excluded, leaving 263 families in the final analysis. Among these parents, 75% said they would have been willing to have their child immunized at the urgent care visit in question if the physician had suggested it. An additional 11% said they would have accepted vaccination if the physician told them that the shot would be safe and strongly encouraged them to accept it. Overall, 86% reported they theoretically would have accepted an immunization during the urgent care visit. In the multivariate analysis, the strongest predictors of stated willingness to accept shots at the urgent care visit were the parent: 1) not being aware that their child was underimmunized (odds ratio [OR] 3.5, 95% confidence interval [CI], 1.6-7.7); 2) perceiving that the child was not very sick at the visit (OR 1.8, 95% CI, 1.1-3.0); 3) being less concerned about the risk of shots (OR 1.8, 95% CI, 1.2-2.5); and 4) being of nonwhite race (OR 3.6, 95% CI, 1.6-7.7). Income and education were not significantly associated with reported willingness to accept immunization. CONCLUSIONS: We conclude that most parents of underimmunized toddlers report being willing to accept immunizations during urgent care visits if the clinician recommends it. More effective ways of alerting providers in urgent care settings when immunizations are due, such as indications on a chart or registration form, hold promise for improving immunization coverage rates.
Clinical outcomes and maternal perceptions of an updated model of perinatal care.
BACKGROUND: Postpartum hospital stays seem likely to remain limited even under new laws which mandate that insurers cover 48-hour hospitalization after uncomplicated delivery. Clinicians, who are increasingly practicing in capitated arrangements, need better information to maximize clinical benefit to mothers and newborns using finite resources. OBJECTIVE AND INTERVENTIONS: This study's aim was to evaluate the clinical outcomes, patient perceptions, and costs of a revised model of perinatal care services. In this model, a new postpartum care center was established for routine follow-up of newborns within 48 hours after hospital discharge, educational efforts were shifted from the postpartum hospitalization to the prenatal period, and lactation consultant hours were increased. DESIGN AND PARTICIPANTS: Controlled, nonrandomized (double cohort) study that compared mothers and newborns with hospital stays of 48 hours or less during the Baseline Care (preintervention) study period (N = 344) with those under the Revised Care (postintervention) study period (N = 456). SETTING: The Hayward, California, medical center of Kaiser Permanente, a nonprofit health maintenance organization. DATA COLLECTION: Telephone interviews were attempted with all mothers 3 weeks after delivery. Data on rehospitalizations, emergency department (ED) and clinic visits, and costs during the first 14 postpartum days were collected from computerized databases and chart review. OUTCOME MEASURES: The combined clinical outcome was defined as any undesirable health event, including rehospitalization, an ED visit, or an urgent clinic visit by either the mother or newborn within the first 14 days postpartum, or breastfeeding discontinuation within the first 21 days postpartum. Maternal satisfaction and costs were also studied. RESULTS: Of 876 attempted interviews, 800 were completed (91%). Analyses were adjusted for age, race, education, parity, breastfeeding experience, and other relevant variables. Among the interviewed mother-newborn pairs, 45% in the Revised Care group experienced the combined clinical outcome, compared with 52% in the Baseline Care group. Newborns in the Revised Care group (29%) were significantly less likely to make urgent clinic visits during the first 14 days of life than those in the Baseline Care group (36%). There were no differences between groups in newborn ED visits or rehospitalizations, maternal clinical outcomes, or breastfeeding continuation. Mothers in the Revised Care group expressed higher satisfaction with the newborn's care, the amount of information they received about newborn care and breastfeeding, and the amount of help they received with breastfeeding. Planned hospital care, planned follow-up visits, and unplanned care costs decreased by $149 per delivery, while the new prenatal class and increased lactation consultant services cost $58 per delivery, for an estimated overall reduction in cost. CONCLUSIONS: We conclude that the revised model of perinatal care in this health maintenance organization medical center improved clinical outcomes and maternal satisfaction for low-risk mothers and newborns without increasing costs.
Evidence on office-based interventions to improve childhood immunization delivery.
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Issues in studying the effectiveness of health services for children.
OBJECTIVES: To discuss issues in studying the effectiveness of health services for children, suggest areas in which more research is needed, and recommend strategies for future research. PRINCIPAL FINDINGS: Issues that should be considered include the choice of perspective, which will help determine the interventions studied and the measures of effectiveness and cost-effectiveness chosen. Unique challenges in this area include the fact that serious measurable morbidity is relatively uncommon in children, that causal relationships between services and outcomes may be difficult to establish, and that standard measures of cost-effectiveness may fail to accurately measure important benefits, such as reduced parental anxiety. More research is needed on high-risk and health-promoting behaviors, on critical parent behaviors, on classifying children by vulnerability status, on modes of delivery of preventive care, and on violence prevention. RECOMMENDATIONS: Group-randomized designs and observational research designs that take advantage of natural variations in practice may be increasingly useful in effectiveness studies. Parent- and patient-reported measures of health status and quality of life should be made briefer and more practical for routine use, and better measures of cost-effectiveness are needed. Future research efforts can best be supported by the concerted efforts of various constituencies, including health plans, providers, patients, researchers, and the government.
Projected cost-effectiveness of primary angioplasty for acute myocardial infarction.
OBJECTIVES: This study sought to evaluate the cost-effectiveness of primary angioplasty for acute myocardial infarction under varying assumptions about effectiveness, existing facilities and staffing and volume of services. BACKGROUND: Primary angioplasty for acute myocardial infarction has reduced mortality in some studies, but its actual effectiveness may vary, and most U.S. hospitals do not have cardiac catheterization laboratories. Projections of cost-effectiveness in various settings are needed for decisions about adoption. METHODS: We created a decision analytic model to compare three policies: primary angioplasty, intravenous thrombolysis and no intervention. Probabilities of health outcomes were taken from randomized trials (base case efficacy assumptions) and community-based studies (effectiveness assumptions). The base case analysis assumed that a hospital with an existing laboratory with night/weekend staffing coverage admitted 200 patients with a myocardial infarction annually. In alternative scenarios, a new laboratory was built, and its capacity for elective procedures was either 1) needed or 2) redundant with existing laboratories. RESULTS: Under base case efficacy assumptions, primary angioplasty resulted in cost savings compared with thrombolysis and had a cost of $12,000/quality-adjusted life-year (QALY) saved compared with no intervention. In sensitivity analyses, when there was an existing cardiac catheterization laboratory at a hospital with > or = 200 patients with a myocardial infarction annually, primary angioplasty had a cost of < $30,000/QALY saved under a wide range of assumptions. However, the cost/QALY saved increased sharply under effectiveness assumptions when the hospital had < 150 patients with a myocardial infarction annually or when a redundant laboratory was built. CONCLUSIONS: At hospitals with an existing cardiac catheterization laboratory, primary angioplasty for acute myocardial infarction would be cost-effective relative to other medical interventions under a wide range of assumptions. The procedure's relative cost-ineffectiveness at low volumes or redundant laboratories supports regionalization of cardiac services in urban areas. However, approaches to overcoming competitive barriers and close monitoring of outcomes and costs will be needed.
Computer-generated recall letters for underimmunized children: how cost-effective?
OBJECTIVE: To evaluate the effectiveness and cost effectiveness of computer-generated recall letters to parents of children overdue for immunizations. METHODS: This randomized controlled trial included children of two facilities in a regional health maintenance organization. Parents of 20-month-olds who had not yet received a measles-mumps-rubella (MMR) immunization were identified via a computerized immunization tracking system. One half were mailed personalized letters that included the recommended immunization schedule and a request to call for an appointment; the other half served as a control group. Receipt of the MMR between 20 and 24 months of age was evaluated with the computerized tracking system. A telephone survey was conducted with parents whose children had not received the MMR by 24 months. Decision analysis was used to project the theoretical outcomes and costs of a recall letter policy for other populations. RESULTS: Among 20-month-old children 10% had not received the MMR; 289 families were included in the analysis. Of families who were mailed letters, 54% (82 of 153) received the MMR by 24 months of age, compared with 35% (47 of 136) of those in the control group (P = 0.001). The telephone survey was completed with 110 parents of children who still did not appear on the health plan computer as having received the MMR by 24 months. Fifteen percent said the child had received an immunization at an outside provider, and of the rest 62% said they had not been aware that an immunization was due. In the cost effectiveness analysis it was projected that recall letters would increase the immunization rate for the regional population of approximately 30000 children from 86% to 90% at a total cost of $5031 annually. The cost per additional child appropriately immunized was $4.04. In sensitivity analyses this cost effectiveness ratio varied depending on the baseline population coverage rate as well as the estimated effectiveness of recall letters. CONCLUSIONS: Computer-generated letters to recall children overdue for immunizations resulted in a higher proportion of children appropriately immunized in this setting. However, the strategy was not as cost-effective as intuition might suggest. Further studies in health maintenance organization (HMO) settings should compare the cost effectiveness of letters with other low cost strategies including automated telephone reminders.
Outpatient management practices associated with reduced risk of pediatric asthma hospitalization and emergency department visits.
OBJECTIVES: Effective outpatient care is believed to prevent hospitalization and emergency department (ED) visits resulting from childhood asthma. The aim of this study was to suggest priority areas for intervention by identifying outpatient management practices associated with the risk of these adverse outcomes in a large population. METHODS: This case-control study included children aged 0 to 14 years with asthma who were members of a regional health maintenance organization. Cases were children undergoing either a hospitalization or an ED visit for asthma during the study period. Control subjects were children with asthma without a hospitalization or an ED visit during the study period who were matched to patients on age, gender, and number of asthma-related hospitalizations in the past 24 months. Data on provider and parent asthma management practices were collected using chart review, closed-ended telephone interviews with parents, and computerized use databases. Multivariate analyses were conducted using conditional logistic regression models. RESULTS: Data were collected on 508 cases and 990 control subjects. A total of 43% of cases were reported by their parents to have moderately severe or severe asthma, compared with 20% of control subjects. Parents of cases with hospitalization were less likely than control subjects to have a written asthma management plan (44% vs 51%) and to report washing bedsheets in hot water at least twice a month (77% vs 86%). Cases with hospitalization were more likely to have a nebulizer (74% vs 56%). In the final multivariate model, race/ethnicity was not associated with having had either a hospitalization or an ED visit, as was lower socioeconomic status. Having a written asthma management plan [odds ratio (OR): 0.54; 95% confidence interval (CI): 0.30, 0.99] and washing bedsheets in hot water at least twice a month (OR: 0.45; 95% CI: 0.21, 0.94) were associated with reduced odds of hospitalization. Having a written asthma management plan (OR: 0.45; 95% CI: 0.27, 0.76) and starting or increasing medications at the onset of a cold or flu were associated with reduced odds of making an ED visit. CONCLUSIONS: Practices that support early intervention for asthma flare-ups by parents at home, particularly written management plans, are strongly associated with reduced risk of adverse outcomes among children with asthma.
Blood lead testing by pediatricians: practice, attitudes, and demographics.
OBJECTIVES: This study aimed to evaluate adherence and identify ways to improve concordance between blood lead testing guidelines and practice. METHODS: One hundred fifty-five pediatricians responded to a questionnaire assessing demographic, knowledge, and attitudinal factors relating to lead testing. RESULTS: Only 27% of the respondents adhered to the guidelines, and less than half knew all of the answers to three factual questions about the recommendations. Adherence was higher among physicians who knew the guidelines, were more recently trained, or had high proportions of Medicaid or minority patients. CONCLUSIONS: Physician education and financial incentives hold the most promise for increasing adherence to blood lead testing guidelines.
Primary angioplasty and thrombolysis for acute myocardial infarction: an evidence summary.
Coronary angioplasty is being increasingly used as the primary treatment for patients with acute myocardial infarction, but controversy remains over its potential adoption in preference to thrombolysis as standard care. This report summarizes the published evidence on health outcomes after primary angioplasty compared with thrombolysis or no intervention for patients with acute myocardial infarction. The data tables presented provide the scientific groundwork to assist physicians and other policy-makers in deciding which interventions to provide for broad populations of patients.
Initial cost of primary angioplasty for acute myocardial infarction.
OBJECTIVES: We sought to evaluate the initial economic cost of primary angioplasty for acute myocardial infarction under varying assumptions about whether a cardiac catheterization laboratory exists, whether services are provided during night and weekend hours and how cardiovascular surgical backup is arranged. BACKGROUND: Primary angioplasty for acute myocardial infarction has resulted in clinical outcomes superior or equal to those obtained with thrombolysis in recent studies, but its future implementation depends greatly on its cost and cost-effectiveness. There is a gap in knowledge about the true economic costs of this procedure, and understanding costs under a variety of hypothetic scenarios is important in planning whether and how the procedure should be offered to broad groups of patients. METHODS: A generalizable spreadsheet model was constructed to calculate the cost of primary angioplasty at a single hospital with assumptions based on data from a large nonprofit health maintenance organization (Kaiser Permanente). The following baseline assumptions were made: 1) A total of 200 patients with myocardial infarction presented to the hospital each year; 2) primary angioplasty was offered for 10 years; 3) the hospital had a cardiac catheterization laboratory; 4) costs of night call for technical personnel and cardiovascular surgical backup were already covered. Other scenarios were modeled to represent different assumptions about existing resources. RESULTS: Under the baseline assumptions, primary angioplasty cost $1,597/procedure. If night call for technical personnel were a new expense, the average cost would be > or = $3,206. If a new cardiac catheterization laboratory needed to be built, costs would range from $3,866 to $14,339/procedure, depending on how cardiovascular surgical backup was provided. Results were sensitive to assumptions about the annual volume of myocardial infarctions, the number of years the procedure was offered and the costs of labor, construction and equipment. CONCLUSIONS: The initial cost of providing primary angioplasty for acute myocardial infarction varies greatly, depending on the setting in which it is provided. To provide information for clinical policy decisions, a cost-effectiveness model is needed that combines these initial costs with data on survival, quality of life and rates and costs of subsequent cardiac procedures.
Would better adherence to guidelines improve childhood immunization rates?
OBJECTIVE: To evaluate the contribution of three provider practices to underimmunization of children with financial coverage for vaccines. DESIGN: Retrospective cohort study of children in a large health maintenance organization, based on computerized databases and chart review. SETTING: Large health maintenance organization in northern California. PATIENTS: The population included 24,268 children who had at least one immunization recorded in the health plan tracking system and had continuous health plan membership between 15 and 24 months of age in 1992 through 1993. The study group (N = 4691) were those who had missed one or more of the immunizations due during their second year. RESULTS: Most (57%) of the underimmunized children had made at least one clinic visit between 15 and 24 months of age. Among those underimmunized children who made well care visits, 90% had been partially immunized at the visit but had not been simultaneously given all vaccines for which they were eligible. When a provider did not give all possible vaccines simultaneously, there was a 9% chance that the child would go on to miss the remaining immunization. Simultaneous administration alone would have achieved full second year coverage of 30% of the underimmunized children in this population. Most underimmunized children (53%), including 35% of those children who had not made any well care visits, had made urgent visits between 15 and 24 months of age. Chart review of randomly sampled patients showed no obstacle or contraindication to immunization at 79% of urgent visits and at 71% of well care visits at which vaccines were withheld. A policy to use weekday urgent visits to promote immunization could potentially reach 27% of the underimmunized children. CONCLUSIONS: Provider practices play an important role in underimmunization of children who have insurance coverage for vaccines. Of the three guidelines evaluated, simultaneous administration of all possible vaccines has the greatest potential effectiveness to improve coverage rates in this population. Other guidelines, such as immunizing at urgent visits, are potentially effective but their costs and logistics need further study.
Cost-effectiveness of varicella serotesting versus presumptive vaccination of school-age children and adolescents.
OBJECTIVE: To evaluate the cost-effectiveness of presumptive vaccination versus serological testing of school-age children (6 to 12 years) and adolescents (13 to 17 years) with a negative or uncertain history of varicella. DESIGN: Decision analysis model based on published and unpublished probabilities and costs. PATIENTS: Hypothetical cohorts of 10,000 school-age children and 10,000 adolescents. MAIN OUTCOME MEASURES: Number of chicken pox cases prevented and cost per chicken pox case prevented. RESULTS: For school-age children, presumptively vaccinating would prevent 95% of the predicted chicken pox cases, would result in net savings when long-term and work loss costs were included, and would have a similar cost per case prevented as routinely testing before vaccination. For adolescents, presumptively vaccinating would be the most effective policy, and would prevent 99% of the projected chicken pox cases. A policy of routinely testing before vaccination would be the least effective policy for adolescents, preventing 81% of the predicted cases. However, even when long-term and work loss costs were taken into account, presumptively vaccinating adolescents had a relatively high cost of $329 per chicken pox case prevented and extremely high incremental costs per chicken pox case prevented compared with policies that involved serological testing. Results for school-age children were sensitive to the probability of previously having had chicken pox given a negative or uncertain history, to the rate of adherence to follow-up visits, and to vaccine price and test price. Results for adolescents were sensitive only to the rate of adherence to the first follow-up visit. CONCLUSIONS: Presumptively vaccinating all patients with a negative or uncertain history of varicella is projected to be a relatively cost-effective policy for school-age children but not for adolescents. However, further empirical studies of the accuracy of a negative or uncertain history of chicken pox in these age groups are needed.
Theoretical epidemiologic and morbidity effects of routine varicella immunization of preschool children in the United States.
The authors studied the effects of routine varicella immunization of US preschool children and of implementation of a catch-up program in older children on the age distribution of cases and on overall morbidity, with emphasis on the sensitivity of the results to level of vaccine coverage, duration of protection, responsiveness to boosting, relative residual susceptibility and infectiousness, and degree of morbidity among vaccine breakthrough cases. An age-structured theoretical transmission model was used, with values for vaccine efficacy based on a review of the literature by an expert panel. Although implementation of a vaccination program resulted in a shift in the age distribution of remaining varicella cases toward older ages with higher complication rates, the overall reduction in cases resulted in decreased morbidity as measured by overall number of hospitalizations and number of primary cases. Routine immunization with live-virus varicella vaccine would probably result in a substantial reduction in the number of uncomplicated primary cases of chickenpox, as well as a decreased number of complicated cases requiring hospitalization. The number and age distribution of vaccinated cases would depend strongly on the characteristics of the vaccine. Vaccine efficacy studies in the field should be designed to obtain better estimates of residual susceptibility, residual infectiousness, duration of protection, and effects of boosting by wild-type reinfection.