Impact of universal varicella vaccination on the use and cost of antibiotics and antivirals for varicella management in the United States.

BACKGROUND: Our objective was to estimate the impact of universal varicella vaccination (UVV) on the use and costs of antibiotics and antivirals for the management of varicella among children in the United States (US). METHODS: A decision tree model of varicella vaccination, infections and treatment decisions was developed. Results were extrapolated to the 2017 population of 73.5 million US children. Model parameters were populated from published sources. Treatment decisions were derived from a survey of health care professionals' recommendations. The base case modelled current vaccination coverage rates in the US with additional scenarios analyses conducted for 0%, 20%, and 80% coverage and did not account for herd immunity benefits. RESULTS: Our model estimated that 551,434 varicella cases occurred annually among children ≤ 18 years in 2017. Antivirals or antibiotics were prescribed in 23.9% of cases, with unvaccinated children receiving the majority for base case. The annual cost for varicella antiviral and antibiotic treatment was approximately $14 million ($26 per case), with cases with no complications accounting for $12 million. Compared with the no vaccination scenario, the current vaccination rates resulted in savings of $181 million (94.7%) for antivirals and $78 million (95.0%) for antibiotics annually. Scenario analyses showed that higher vaccination coverage (from 0% to 80%) resulted in reduced annual expenditures for antivirals (from $191 million to $41 million), and antibiotics ($82 million to $17 million). CONCLUSIONS: UVV was associated with significant reductions in the use of antibiotics and antivirals and their associated costs in the US. Higher vaccination coverage was associated with lower use and costs of antibiotics and antivirals for varicella management.

The impact of long-term moderate level of vaccination coverage for epidemiology of varicella in Lu'an, China: should we change immunisation strategy now?

As China implements the voluntary vaccination programme of one-dose of varicella vaccine (VarV) for decades, robust estimates of the impact of voluntary vaccination era on epidemiology of varicella are needed. We estimated the vaccination coverage (VC) of VarV by using surveillance data on immunisation. The descriptive epidemiological method was used to describe the changing epidemiology of varicella from 2007 to 2018. The screening method was used to estimate the vaccine effectiveness (VE) of VarV. The overall VC for VarV was 71.7%, ranged from 47.7% to 79.5% among 2008-2017 birth cohorts. In total, 16 660 varicella cases were reported during 2007-2018, the incidence increased from 10.0 cases per 100 000 population in 2007 to 65.2 cases per 100 000 population in 2018. A shift in age group of varicella was observed since 2012, with the age increased from 5-9 years to 10-14 years. The overall VE was 79.9%, and the VE increased from 60.1% in 2008 birth cohort to 96.2% in 2017 birth cohort. We found that the overall VE for VarV is moderate, but appears highly effective within 5 years after vaccination. In addition, a shift varicella infection to older ages has occurred at the long-term moderate level VC of one-dose VarV. Therefore, to contain the incidence of varicella and prevent any potential shift to older ages, the introduction of VarV into routine immunisation programme is likely needed in Lu'an.

Measuring Infection Transmission in a Stochastic SIV Model with Infection Reintroduction and Imperfect Vaccine.

An additional compartment of vaccinated individuals is considered in a SIS stochastic epidemic model with infection reintroduction. The quantification of the spread of the disease is modeled by a continuous time Markov chain. A well-known measure of the initial transmission potential is the basic reproduction number [Formula: see text], which determines the herd immunity threshold or the critical proportion of immune individuals required to stop the spread of a disease when a vaccine offers a complete protection. Due to repeated contacts between the typical infective and previously infected individuals, [Formula: see text] overestimates the average number of secondary infections and leads to, perhaps unnecessary, high immunization coverage. Assuming that the vaccine is imperfect, alternative measures to [Formula: see text] are defined in order to study the influence of the initial coverage and vaccine efficacy on the transmission of the epidemic.

Frequency and cost of live vaccines administered too soon after prior live vaccine in children aged 12 months through 6 years, 2014-2017.

OBJECTIVE: To identify number of children who received live vaccines outside recommended intervals between doses and calculate corrective revaccination costs. METHODS: We analyzed >1.6 million vaccination records for children aged 12 months through 6 years from six immunization information system (IIS) Sentinel Sites from 2014-15 when live attenuated influenza vaccine (LAIV, FluMist® Quadrivalent) was recommended for use, and from 2016-17, when not recommended for use. Depending on the vaccine, insufficient intervals between live vaccine doses are less than 24 or 28 days from a preceding live vaccine dose. Private and public purchase costs of vaccines were used to determine revaccination costs of live vaccine doses administered during the live vaccine conflict interval. Measles, mumps, rubella (MMR), varicella, combined MMRV, and LAIV were live vaccines evaluated in this study. RESULTS: Among 946,659 children who received at least one live vaccine dose from 2014-15, 4,873 (0.5%) received at least one dose too soon after a prior live vaccine (revaccination cost, $786,413) with a median conflict interval of 16 days. Among 704,591 children who received at least one live vaccine dose from 2016-17, 1,001 (0.1%) received at least one dose too soon after a prior live vaccine (revaccination cost, $181,565) with a median conflict interval of 14 days. The live vaccine most frequently administered outside of the recommended intervals was LAIV from 2014-15, and varicella from 2016-17. CONCLUSIONS: Live vaccine interval errors were rare (0.5%), indicating an adherence to recommendations. If all invalid doses were corrected by revaccination over the two time periods, the cost within the IIS Sentinel Sites would be nearly one million dollars. Provider awareness about live vaccine conflicts, especially with LAIV, could prevent errors, and utilization of clinical decision support functionality within IISs and Electronic Health Record Systems can facilitate better vaccination practices.

Chickenpox: An update.

Despite its benign characteristics, chickenpox is a childhood disease responsible for complications and deaths, particularly in the high-risk population. VariZIG®, not commercialized in France, is a good alternative for seronegative individuals exposed to the virus and not eligible for vaccination. The efficacy of routine vaccination has been demonstrated with a decrease in chickenpox incidence and with the development of herd immunity. Over time, the protective antibody titer of vaccinated people decreases and can be maintained by two doses of the vaccine. A tetravalent measles-mumps-rubella-chickenpox vaccine, used in the United States, has a good tolerability in spite of the occurrence of fever and febrile seizures. Routine vaccination would contribute to make savings in France, by reducing direct and indirect costs of chickenpox.

The impact of demographic changes, exogenous boosting and new vaccination policies on varicella and herpes zoster in Italy: a modelling and cost-effectiveness study.

BACKGROUND: The present study aims to evaluate the cost-effectiveness of the newly introduced varicella and herpes zoster (HZ) vaccination programmes in Italy. The appropriateness of the introduction of the varicella vaccine is highly debated because of concerns about the consequences on HZ epidemiology and the expected increase in the number of severe cases in case of suboptimal coverage levels. METHODS: We performed a cost-utility analysis based on a stochastic individual-based model that considers realistic demographic processes and two different underlying mechanisms of exogenous boosting (temporary and progressive immunity). Routine varicella vaccination is given with a two-dose schedule (15 months, 5-6 years). The HZ vaccine is offered to the elderly (65 years), either alone or in combination with an initial catch-up campaign (66-75 years). The main outcome measures are averted cases and deaths, costs per quality-adjusted life years gained, incremental cost-effectiveness ratios, and net monetary benefits associated with the different vaccination policies. RESULTS: Demographic processes have contributed to shaping varicella and HZ epidemiology over the years, decreasing varicella circulation and increasing the incidence of HZ. The recent introduction of varicella vaccination in Italy is expected to produce an enduring reduction in varicella incidence and, indirectly, a further increase of HZ incidence in the first decades, followed by a significant reduction in the long term. However, the concurrent introduction of routine HZ vaccination at 65 years of age is expected to mitigate this increase and, in the longer run, to reduce HZ burden to its minimum. From an economic perspective, all the considered policies are cost-effective, with the exception of varicella vaccination alone when considering a time horizon of 50 years. These results are robust to parameter uncertainties, to the two different hypotheses on the mechanism driving exogenous boosting, and to different demographic projection scenarios. CONCLUSIONS: The recent introduction of a combined varicella and HZ vaccination programme in Italy will produce significant reductions in the burden of both diseases and is found to be a cost-effective policy. This programme will counterbalance the increasing trend of zoster incidence purely due to demographic processes.

Economic burden of varicella in children 1-12 Years of age in Hungary, 2011-2015.

BACKGROUND: Although live-attenuated varicella-zoster virus (VZV) vaccines have been proven to be safe and effective in preventing varicella and real-word evidence shows routine childhood immunization programs are effective in dramatically reducing varicella associated morbidity and mortality, varicella vaccine is not included in the National Immunization Program (NIP) in Hungary. The purpose of this study was to evaluate the clinical and economic burden associated with varicella in Hungary. METHODS: This was a multicenter, retrospective, chart review study of patients aged 1-12 years with a primary varicella diagnosis between 2011 and 2015. Healthcare resource utilization (HCRU) associated with varicella, unit costs, and work loss were used to estimate direct and indirect costs. All costs are presented in 2015 HUF / Euros (€). RESULTS: 156 children with varicella were included (75 outpatients, 81 inpatients), with a mean age of 4.4 (SD: 2.0) and 3.7 (SD: 2.1) years, respectively. One or more complications were reported by 12.0% of outpatients and 92.6% of inpatients, the most common being dehydration, skin and soft tissue infections, pneumonia, keratoconjunctivitis, and cerebellitis. HCRU estimates included use of over-the-counter (OTC) medications (96.0% outpatients, 53.1% inpatients), prescription medications (9.3% outpatients, 70.4% inpatients), tests/procedures (4.0% outpatients, 97.5% inpatients), and consultation with allied health professionals (2.7% outpatients, 30.9% inpatients). The average duration of hospital stay (inpatients) was 3.6 (95% CI: 3.2, 4.1) days. The total combined direct and indirect cost per varicella case was 228,146.7 Hungarian Forint (HUF)/€ 736.0 for inpatients and 49,790.6 HUF/€ 106.6 for outpatients. The overall annual cost of varicella in Hungary for children aged <15 years in 2015 was estimated at 1,903,332,524.3 HUF/ € 6,139,980.4. CONCLUSION: Varicella is associated with substantial clinical burden in Hungary, resulting in the utilization of a significant amount of healthcare resources. These results support the need for routine vaccination of all healthy children to reduce the varicella-associated disease burden.

Coverage, efficacy or dosing interval: which factor predominantly influences the impact of routine childhood vaccination for the prevention of varicella? A model-based study for Italy.

BACKGROUND: Varicella is a highly infectious disease with a significant public health and economic burden, which can be prevented with childhood routine varicella vaccination. Vaccination strategies differ by country. Some factors are known to play an important role (number of doses, coverage, dosing interval, efficacy and catch-up programmes), however, their relative impact on the reduction of varicella in the population remains unclear. This paper aims to help policy makers prioritise the critical factors to achieve the most successful vaccination programme with the available budget. METHODS: Scenarios assessed the impact of different vaccination strategies on reduction of varicella disease in the population. A dynamic transmission model was used and adapted to fit Italian demographics and population mixing patterns. Inputs included coverage, number of doses, dosing intervals, first-dose efficacy and availability of catch-up programmes, based on strategies currently used or likely to be used in different countries. The time horizon was 30 years. RESULTS: Both one- and two-dose routine varicella vaccination strategies prevented a comparable number of varicella cases with complications, but two-doses provided broader protection due to prevention of a higher number of milder varicella cases. A catch-up programme in susceptible adolescents aged 10-14 years old reduced varicella cases by 27-43 % in older children, which are often more severe than in younger children. Coverage, for all strategies, sustained at high levels achieved the largest reduction in varicella. In general, a 20 % increase in coverage resulted in a further 27-31 % reduction in varicella cases. When high coverage is reached, the impact of dosing interval and first-dose vaccine efficacy had a relatively lower impact on disease prevention in the population. Compared to the long (11 years) dosing interval, the short (5 months) and medium (5 years) interval schedules reduced varicella cases by a further 5-13 % and 2-5 %, respectively. Similarly, a 10 % increase in first-dose efficacy (from 65 to 75 % efficacy) prevented 2-5 % more varicella cases, suggesting it is the least influential factor when considering routine varicella vaccination. CONCLUSIONS: Vaccination strategies can be implemented differently in each country depending on their needs, infrastructure and healthcare budget. However, ensuring high coverage remains the critical success factor for significant prevention of varicella when introducing varicella vaccination in the national immunisation programme.

Increasing incidence associated with herpes zoster infection in British Columbia, Canada.

BACKGROUND: Recent studies have shown an increasing incidence of herpes zoster (HZ) infection, which may be related to the introduction of varicella vaccination programs in children. We examined the epidemiology and treatment costs of HZ and post-herpetic neuralgia (PHN) over time in British Columbia, Canada. METHODS: The cohort consisted of all cases with HZ infection from January 1, 1997 and December 31, 2012. Incident zoster was defined as a case (ICD-9 053 or ICD-10 B02) without a previous episode of HZ or PHN in the previous 12 months. We determined the incidence for HZ and PHN and the age-sex standardized rate for the overall population. We determined the association between the varicella vaccination program and increased HZ rates by evaluating the rate ratios in the publicly-funded varicella vaccine period compared to the non-publicly funded period in a regression model. We evaluated the hospitalization rates, treatment by GPs and their associated yearly costs for HZ and PHN. RESULTS: HZ incidence increased for the entire study period from 3.2 per 1000 population in 1997 to 4.5 in 2012. HZ rates were higher for females than males and all age groups had an increased incidence rate, except the 0-9 year olds, where the rate decreased. Crude and age-sex standardized incidence rates of PHN demonstrated very similar patterns to HZ incidence. Based on the regression model, rates of HZ were higher in the older individuals. No significant increase with HZ incidence was seen during the publically funded varicella vaccination program compared to the non-publicly funded period. From 1997 to 2012, the annual HZ-related costs associated with hospitalizations and GP visits were over $CDN4.9 million and $CDN537,286, respectively; treatment costs for hospitalizations have increased significantly over time. Majority of PHN-related cases are managed by GPs, with a steady increase over time in number of cases and associated annual costs. CONCLUSIONS: The incidence of zoster and PHN is increasing with time, particularly in the elderly population and the risk is greater in the over 65 year olds. Treatment costs for both HZ and PHN represent a significant burden on the Canadian healthcare system.

Varicella immunization requirements for US colleges: 2014-2015 academic year.

OBJECTIVE: To obtain information on varicella prematriculation requirements in US colleges for undergraduate students during the 2014-2015 academic year. PARTICIPANTS: Health care professionals and member schools of the American College Health Association (ACHA). METHODS: An electronic survey was sent to ACHA members regarding school characteristics and whether schools had policies in place requiring that students show proof of 2 doses of varicella vaccination for school attendance. RESULTS: Only 27% (101/370) of schools had a varicella prematriculation requirement for undergraduate students. Only 68% of schools always enforced this requirement. Private schools, 4-year schools, northeastern schools, those with <5,000 students, and schools located in a state with a 2-dose varicella vaccine mandate were significantly more likely to have a varicella prematriculation requirement. CONCLUSIONS: A small proportion of US colleges have a varicella prematriculation requirement for varicella immunity. College vaccination requirements are an important tool for controlling varicella in these settings.

Vaccination to prevent varicella: Goldman and King's response to Myers' interpretation of Varicella Active Surveillance Project data.

BACKGROUND: There is increasing evidence that herpes zoster (HZ) incidence rates among children and adults (aged <60 years) with a history of natural varicella are influenced primarily by the frequency of exogenous exposures, while asymptomatic endogenous reactivations help to cap the rate at approximately 550 cases/100,000 person-years when exogenous boosting becomes rare. The Antelope Valley Varicella Active Surveillance Project was funded by the Centers for Disease Control and Prevention in 1995 to monitor the effects of varicella vaccination in one of the three representative regions of the United States. The stability in the data collection and number of reporting sites under varicella surveillance from 1995-2002 and HZ surveillance during 2000-2001 and 2006-2007 contributed to the robustness of the discerned trends. DISCUSSION: Varicella vaccination may be useful for leukemic children; however, the target population in the United States is all children. Since the varicella vaccine inoculates its recipients with live, attenuated varicella-zoster virus (VZV), clinical varicella cases have dramatically declined. Declining exogenous exposures (boosts) from children shedding natural VZV have caused waning cell-mediated immunity. Thus, the protection provided by varicella vaccination is neither lifelong nor complete. Moreover, dramatic increases in the incidence of adult shingles cases have been observed since HZ was added to the surveillance in 2000. In 2013, this topic is still debated and remains controversial in the United States. SUMMARY: When the costs of the booster dose for varicella and the increased shingles recurrences are included, the universal varicella vaccination program is neither effective nor cost-effective.

Validity of a reported history of chickenpox in targeting varicella vaccination at susceptible adolescents in England.

INTRODUCTION: In the UK, primary varicella is usually a mild infection in children, but can cause serious illness in susceptible pregnant women and adults. The UK Joint Committee on Vaccination and Immunisation is considering an adolescent varicella vaccination programme. Cost-effectiveness depends upon identifying susceptibles and minimising vaccine wastage, and chickenpox history is one method to screen for eligibility. To inform this approach, we estimated the proportion of adolescents with varicella antibodies by reported chickenpox history. METHODS: Recruitment occurred through secondary schools in England from February to September 2012. Parents were asked about their child's history of chickenpox, explicitly setting the context in terms of the implications for vaccination. 247 adolescents, whose parents reported positive (120), negative (77) or uncertain (50) chickenpox history provided oral fluid for varicella zoster virus-specific immunoglobulin-G (VZV-IgG) testing. RESULTS: 109 (90.8% [85.6-96.0%]) adolescents with a positive chickenpox history, 52 (67.5% [57.0-78.1%]) with a negative history and 42 (84.0% [73.7-94.3%]) with an uncertain history had VZV-IgG suggesting prior infection. Combining negative and uncertain histories, 74% had VZV-IgG (best-case). When discounting low total-IgG samples and counting equivocals as positive (worst-case), 84% had VZV-IgG. We also modelled outcomes by varying the negative predictive value (NPV) for the antibody assay, and found 74-87% under the best-case and 84-92% under the worst-case scenario would receive vaccine unnecessarily as NPV falls to 50%. CONCLUSION: Reported chickenpox history discriminates between varicella immunity and susceptibility in adolescents, but significant vaccine wastage would occur if this approach alone were used to determine vaccine eligibility. A small but important proportion of those with positive chickenpox history would remain susceptible. These data are needed to determine whether reported history, with or without oral fluid testing in those with negative and uncertain history, is sufficiently discriminatory to underpin a cost-effective adolescent varicella vaccination programme.

Vacina Tetraviral (varicela, sarampo, caxumba e rubéola) / Tetraviral vaccine (chickenpox, measles, mumps and rubella)

A infecção pelo vírus varicela-zoster (VVZ) se manifesta por meio de dois quadros clínicos distintos: a infecção primária se manifesta como varicela, após a qual o vírus estabelece latência nos gânglios nervosos da raiz dorsal. Muitos anos após a infecção primária, pode ocorrer a reativação do VVZ, que se manifesta como herpes-zoster. Apenas um sorotipo de VVZ é conhecido e humanos são os únicos reservatórios do vírus, sendo possível o controle da infecção em uma população através de imunização ativa, muito embora o estabelecimento de latência viral e a possibilidade de reativação e transmissão do VVZ a partir de um caso de zoster tornem necessárias a manutenção da vigilância e altas coberturas vacinais enquanto existirem indivíduos com infecção latente pelo vírus selvagem. Abordar de forma adequada as formas complexas de manifestação clínica da infecção pelo VVZ na perspectiva populacional tem se constituído em desafio para os estudos de custo-efetividade da vacina contra varicela. A varicela é doença comum da infância e tem distribuição universal. A grande maioria dos casos ocorre em menores de 15 anos de idade e praticamente todos os adultos já foram infectados por VVZ. A doença apresenta distribuição sazonal, com a maioria dos casos ocorrendo no final do inverno e início da primavera (de julho a novembro, no Brasil). Picos epidêmicos têm sido observados a cada três a cinco anos. O tratamento clínico, na maioria dos casos, se resume ao uso de medicação sintomática, anti-térmicos, anti-sépticos e anti-pruriginosos. Nos casos com infecção bacteriana secundária recomenda-se o uso de antibióticos por via oral, observando-se, na prática clínica habitual nos serviços de saúde, uma variabilidade nas drogas prescritas, com reflexos importantes nos custos do tratamento. A vacinação contra a varicela não está contemplada nos calendários básicos de vacinação (criança, adolescente, adulto e idoso) no Brasil, exceto para situações excepcionais, nas quais se disponibiliza a vacina para grupos com riscos específicos. Apesar desta estratégia cumprir importante papel na proteção individual de pessoas mais vulneráveis, o impacto desta ação é inexistente à proteção da coletividade. Em 2013, com o intuito de ampliar esta proteção, o Ministério da Saúde (MS) pretende incluir as vacinas de varicela e hepatite A no calendário básico de vacinação da criança. Para que ocorra a introdução destas novas vacinas é necessário levar em consideração aspectos importantes como a redução dos custos dos imunobiológicos, logística operacional (armazenamento, transporte, seringas e agulhas), eficácia dos insumos além do custo-benefício desses produtos. Portanto, estudos de avaliação econômica em saúde têm apoiado diretamente a tomada de decisão, demonstrando transparência, perspectivas econômicas e epidemiológicas, promovendo assim a eficiência e equidade. Obedecendo a tais prerrogativas. Foram encomendados e apresentados os estudos de custo-efetividade das vacinas de varicela e hepatite A. Faz-se necessário, também, considerar que com as recentes introduções de novas vacinas nos calendários de vacinação do PNI, a rede de frio encontra-se no seu limite da capacidade instalada, em todos os níveis, de modo que há a necessidade de uma avaliação e readequação dessa rede. A vacina de varicela será introduzida no calendário básico de vacinação, para a população de 1 ano de idade, a partir do uso da vacina combinada tetraviral (sarampo, caxumba, rubéola e varicela), substituindo, portanto, o uso da vacina tríplice viral (sarampo, caxumba e rubéola) nesta população. Os membros da CONITEC presentes na 8ª reunião do plenário do dia 06/09/2012, por unanimidade, ratificaram a decisão de recomendar a incorporação da vacina tetraviral na rotina do Programa Nacional de Imunização. A Portaria CTIE-MS N.º 4 de 18 de janeiro de 2013 - Torna pública a decisão de incorporar a vacina tetraviral (varicela, sarampo, caxumba e rubéola) na rotina do Programa Nacional de Imunização do Sistema Único de Saúde (SUS).

Impact of methodology on the results of economic evaluations of varicella vaccination programs: is it important for decision-making?

This study aims to review the literature on economic evaluation of childhood varicella vaccination programs and to discuss how heterogeneity in methodological aspects and estimation of parameters can affect the studies' results. After applying the inclusion criteria, 27 studies published from 1980 to 2008 were analyzed in relation to methodological differences. There was great heterogeneity in the perspective adopted, evaluation of indirect costs, type of model used, modeling of the effect on herpes zoster, and estimation of vaccine price and efficacy parameters. The factor with the greatest impact on results was the inclusion of indirect costs, followed by the perspective adopted and vaccine price. The choice of a particular methodological aspect or parameter affected the studies' results and conclusions. It is essential that authors present these choices transparently so that users of economic evaluations understand the implications of such choices and the direction in which the results of the analysis were conducted.

Impact of methodology on the results of economic evaluations of varicella vaccination programs: is it important for decision-making? / Impacto da metodologia nos resultados de avaliações econômicas de programas de vacinação da varicela: é importante para o processo de tomada de decisão?

This study aims to review the literature on economic evaluation of childhood varicella vaccination programs and to discuss how heterogeneity in methodological aspects and estimation of parameters can affect the studies' results. After applying the inclusion criteria, 27 studies published from 1980 to 2008 were analyzed in relation to methodological differences. There was great heterogeneity in the perspective adopted, evaluation of indirect costs, type of model used, modeling of the effect on herpes zoster, and estimation of vaccine price and efficacy parameters. The factor with the greatest impact on results was the inclusion of indirect costs, followed by the perspective adopted and vaccine price. The choice of a particular methodological aspect or parameter affected the studies' results and conclusions. It is essential that authors present these choices transparently so that users of economic evaluations understand the implications of such choices and the direction in which the results of the analysis were conducted.

O presente trabalho tem por objetivo rever a literatura sobre avaliação econômica de programas de vacinação infantil contra varicela, e discutir como a heterogeneidade em aspectos metodológicos e na estimativa dos parâmetros pode afetar os resultados dos estudos. Após aplicação dos critérios de inclusão, 27 estudos do período de 1980 a 2008 foram analisados com relação às diferenças metodológicas. Observou-se grande heterogeneidade na perspectiva adotada, valoração dos custos indiretos, tipo de modelo empregado, modelagem do efeito no herpes zoster, e na estimativa dos parâmetros de preço e eficácia da vacina. O fator que mais impactou os resultados foi a inclusão dos custos indiretos seguido da perspectiva e preço de vacina adotados. A escolha de um determinado aspecto metodológico ou parâmetro afetou os resultados e conclusões dos estudos. É de fundamental importância que os autores apresentem essas escolhas com transparência para que os usuários das avaliações econômicas compreendam as repercussões dessas escolhas, e em qual direção os resultados das análises foram conduzidos.

Cost-effectiveness analysis of universal childhood vaccination against varicella in Brazil.

This study conducts a cost-effectiveness analysis of a childhood universal varicella vaccination program in Brazil. An age and time-dependent dynamic model was developed to estimate the incidence of varicella for 30 years. Assuming a single-dose schedule; vaccine efficacy of 85% and coverage of 80%, the program could prevent 74,422,058 cases and 2905 deaths. It would cost R$ 3,178,396,110 and save R$ 660,076,410 to the society and R$ 365,602,305 to the healthcare system. The program is cost-effective (R$ 14,749 and R$ 16,582 per life-year saved under the societal and the healthcare system's perspective, respectively). The program's cost-effectiveness is highly sensitive to the vaccine price and number of doses.

Quality improvement for medicaid members of a commercial health plan: impact on racial/ethnic differences.

OBJECTIVE: To describe one commercial Medicaid Managed Care (MMC) health plan's quality improvement (QI) program that achieved high varicella immunization rates among members of an ethnically diverse population in California. DESIGN: Retrospective study using administrative data. PATIENTS: Blue Cross of California Medicaid enrolled children who turned two years old during each calendar year of the study. INTERVENTION: A specialized immunization strategy was implemented with data collected at three time points, pre-intervention (baseline--1998/1999), two-year followup (2001) and three-year followup (2002). MAIN OUTCOME MEASURE: Varicella vaccination coverage after the QI initiative. RESULTS: A statistically significant increase in varicella immunization rates for the study population was observed between baseline (49.5%) and three-year follow up (89.4%). Baseline differences in immunization rates by physician type and patient ethnicity were reduced. CONCLUSION: Trends in varicella vaccination coverage among members of this commercial MMC plan are in line with trends in overall vaccination coverage in California, indicating that commercial MMC health plans have the capacity to offer accessible and high quality care to ethnically diverse patients to mediate racial/ethnic differences. More work is needed to explore the impact of quality improvement programs of MMC plans in other areas.

Methodological issues in design and analysis of a matched case-control study of a vaccine's effectiveness.

OBJECTIVE: Case-control studies of the effectiveness of a vaccine are useful to answer important questions, such as the effectiveness of a vaccine over time, that usually are not addressed by prelicensure clinical trials of the vaccine's efficacy. This report describes methodological issues related to design and analysis that were used to determine the effects of time since vaccination and age at the time of vaccination. STUDY DESIGN AND SETTING: A matched case-control study of the effectiveness of varicella vaccine was conducted. RESULTS: Sampling procedures and conditional logistic regression models including interaction terms are described. CONCLUSION: Use of these methods will allow investigators to assess the effects of a wide range of variables, such as time since vaccination and age at the time of vaccination, on the effectiveness of a vaccine.

Survey of the status of self-paid varicella vaccination among children one to six years of age in Taiwan.

BACKGROUND AND PURPOSE: Prior to 2004, the mass immunization program in Taiwan did not include varicella vaccine; however, parents could have their children vaccinated by the self-payment option. METHODS: In April 2002, we distributed 1271 questionnaires to the caregivers of children aged 1 to 6 years in Taoyuan county, Taiwan, to survey the status of vaccination rate against varicella, parental attitudes toward self-paid varicella vaccine, and the demographic characteristics of the family. RESULTS: Based on the answers provided in the questionnaires (99% response rate), we learned that until April 2002, the vaccination rate against varicella was 26%. Most children received this vaccine by the age of 1 to 2 years (64%) mainly at local clinics (66%). Majority of the caregivers (94%) would have immunized their children against varicella if the vaccines were freely provided or partially paid for. Caregivers living in the city, those children whose parents had a relatively high education level, those from families with fewer children, those whose children were inoculated with other self-paid vaccines, and those parents with a higher family income were significantly (p<0.0001) willing to have their children inoculated. CONCLUSIONS: In Taiwan, most caregivers were willing to have their children immunized against varicella if the vaccines were freely provided, or even if they were partially paid for. In case of other effective vaccines of high cost and not included in mass immunization, partially paying for the vaccine may be an option, since the parents' willingness was substantially greater when the cost is lowered.