An economic evaluation of universal pertussis vaccination in Italy

Inclusion of the value of herd immunity in economic evaluations of vaccines. A systematic review of methods used

OBJECTIVE

The objectives of this review were to identify vaccine economic evaluations that include herd immunity and describe the methodological approaches used.

METHODS

We used Kim and Goldie's search strategy from a systematic review (1976-2007) of modelling approaches used in vaccine economic evaluations and additionally searched PubMed/MEDLINE and Embase for 2007-2015. Studies were classified according to modelling approach used. Methods for estimating herd immunity effects were described, in particular for the static models.

RESULTS

We identified 625 economic evaluations of vaccines against human-transmissible diseases from 1976 to 2015. Of these, 172 (28%) included herd immunity. While 4% of studies included herd immunity in 2001, 53% of those published in 2015 did this. Pneumococcal, human papilloma and rotavirus vaccines represented the majority of studies (63%) considering herd immunity. Ninety-five of the 172 studies utilised a static model, 59 applied a dynamic model, eight a hybrid model and ten did not clearly state which method was used. Relatively crude methods and assumptions were used in the majority of the static model studies.

CONCLUSION

The proportion of economic evaluations using a dynamic model has increased in recent years. However, 55% of the included studies used a static model for estimating herd immunity. Values from a static model can only be considered reliable if high quality surveillance data are incorporated into the analysis. Without this, the results are questionable and they should only be included in sensitivity analysis.

Cost-effectiveness of adolescent pertussis vaccination for the Netherlands: using an individual-based dynamic model

BACKGROUND

Despite widespread immunization programs, a clear increase in pertussis incidence is apparent in many developed countries during the last decades. Consequently, additional immunization strategies are considered to reduce the burden of disease. The aim of this study is to design an individual-based stochastic dynamic framework to model pertussis transmission in the population in order to predict the epidemiologic and economic consequences of the implementation of universal booster vaccination programs. Using this framework, we estimate the cost-effectiveness of universal adolescent pertussis booster vaccination at the age of 12 years in the Netherlands.

METHODS/PRINCIPAL FINDINGS

We designed a discrete event simulation (DES) model to predict the epidemiological and economic consequences of implementing universal adolescent booster vaccination. We used national age-specific notification data over the period 1996-2000--corrected for underreporting--to calibrate the model assuming a steady state situation. Subsequently, booster vaccination was introduced. Input parameters of the model were derived from literature, national data sources (e.g. costing data, incidence and hospitalization data) and expert opinions. As there is no consensus on the duration of immunity acquired by natural infection, we considered two scenarios for this duration of protection (i.e. 8 and 15 years). In both scenarios, total pertussis incidence decreased as a result of adolescent vaccination. From a societal perspective, the cost-effectiveness was estimated at €4418/QALY (range: 3205-6364 € per QALY) and €6371/QALY (range: 4139-9549 € per QALY) for the 8- and 15-year protection scenarios, respectively. Sensitivity analyses revealed that the outcomes are most sensitive to the quality of life weights used for pertussis disease.

CONCLUSIONS/SIGNIFICANCE

To our knowledge we designed the first individual-based dynamic framework to model pertussis transmission in the population. This study indicates that adolescent pertussis vaccination is likely to be a cost-effective intervention for The Netherlands. The model is suited to investigate further pertussis booster vaccination strategies.

The use of modeling in the economic evaluation of vaccines

As a consequence of the increased role of pharmacoeconomics in policy-making, economic evaluations are performed at more and more early stages in the development of a therapeutic. This implies the development of models to assess the future impact of an intervention and to account for the level of uncertainty in the associated parameters. This also applies for economic evaluations of vaccines, where not only progression of disease and associated costs are important, but the transmission of the causing agent in the target population also has to be modelled. In this review, we provide an overview of the models that have been used in recent publications on the pharmacoeconomics of vaccines and go deeper into some of the methodological issues associated with the use of models in the economic evaluation of vaccines.

In or out? Income losses in health state valuations: a review

BACKGROUND

In 1996 the Washington Panel controversially recommended valuing productivity costs (PC) in terms of quality-adjusted life years. The Panel's assumption that respondents in health state valuation (HSV) exercises take income losses into account could not be countered since there was no evidence regarding what people consider in HSV exercises. If they do consider income losses and if this changes HSVs, then all economic evaluations that have included PC in the numerator may have double-counted these costs. Alternatively, if respondents do not consider income losses then all past economic evaluations that have not included PC in the numerator have failed to account for sizeable societal costs.

OBJECTIVES

Through a review we aim to recapture the debate surrounding the appropriate method for including PC in health economic evaluations, to identify empirical evidence addressing the assumptions of the Panel, and recommend a future research agenda.

METHODS

Through a review we identify, outline, and critically appraise the existing empirical studies that attempt to address whether respondents include income effects in HSV exercises.

RESULTS AND CONCLUSION

Seven empirical studies were identified. Overall, it seems that not explicitly mentioning the inclusion of income will induce a minority of respondents to include these effects and this appears not to influence results. More empirical work is needed, using generic instruments, larger samples, and using the interview method of administration.

The cost of epidemiological transition: a study of a decrease in pertussis vaccination coverage

Based on a transfer function intervention model applied to epidemiological data of pertussis incidence and pertussis vaccination in England and Wales, the consequences of pertussis vaccination strategies were estimated in terms of health effects and economic direct costs. It was established that sixth dose pertussis vaccination programs at 90% coverage were the most cost saving for short-term and for long-term vaccination prevention strategies. We considered two alternative strategies with whole-cell or acellular vaccines for primary course and acellular vaccine for two booster doses in children and one booster in adolescents. As a rule, programs based on exclusive use of acellular vaccines for all the doses were more expensive. Direct costs of programs with the vaccination rate at 90% remained systematically lower than the expected cost of pertussis disease in the case of non prevention. The stability over time of the vaccination coverage at a constant level of 90% made it possible to ensure the largest cost saving strategy during the period of 14 years of analysis. Transitions to programs with a lower proportion of vaccinated children systematically incurred an incremental direct cost for society. The amount of that cost rose with the size of the drop in the new vaccination coverage and diminished, due to the J-curve optimistic effect, when the fall in vaccination rate generated a delayed increase in notification cases of pertussis.

Cost-effectiveness of universal pneumococcal vaccination for infants in Italy

This study aimed at estimating the health and economic outcomes of universal infant vaccination with seven-valent pneumococcal conjugate vaccine (PCV-7) in Italy. A Markov model simulated lifetime evolution of a birth cohort (538,138 children): universal vaccination would avert 769 invasive infections, 18 deaths and 1323 life years. At base-case analysis, universal three-dose vaccination would cost euro 26,449 (95% CI: 1975-62,075) and euro 38,286 (95% CI: 22,164-70,801) per life year-saved in the societal and the NHS perspective, respectively. In the hypothesis of a 5-year long protection period, vaccination would cost euro 32,694 and euro 43,115 per life-year saved. Considering yearly incidence of invasive pneumococcal disease reported for Veneto and Sardinia regions, PCV-7 vaccination would result highly cost-effective determining a cost of euro 10,479 and euro 16,890 per life year-save in the NHS and the societal perspective, respectively.

Economic burden of pertussis and the impact of immunization

Although routine use of vaccines has diminished the incidence of pertussis disease, it has not eliminated the pathogen. Epidemiologic data confirm that pertussis remains a significant health problem in all age groups. Disease burden is highest in infants, in whom pertussis disease frequently leads to severe complications and mortality, although it is also a significant health burden in adolescents and adults, in whom the reported incidence of pertussis is increasing. The Global Pertussis Initiative reviewed the literature to find data that express the economic impact of this health burden and to review economic evaluations of pertussis immunization. Although only limited data on the direct and indirect costs of pertussis are available, they suggest that it poses a significant economic burden and indicate that the direct medical costs of pertussis depend on the rate of hospitalization and the severity of complications, and are highest in infants. The indirect costs of pertussis also appear to be considerable, particularly among adults, in whom the disease reduces work productivity, because of either personal illness or child care responsibilities. Several health economic models on the cost effectiveness of childhood immunization strategies have been published, and although constrained by missing data, have generally found childhood immunization strategies to be cost-effective. Economic analyses of adolescent and adult immunization strategies have also been conducted, but the findings of these studies have been inconsistent. The most recent evaluations, using much higher estimates of incidence than reported previously, suggest that immunization of adolescents and specific adult subgroups may be cost-effective. The literature review confirmed that the economic burden of pertussis is substantial, but there are gaps in existing information. In the short term, further economic analyses are required, particularly of adolescent and adult immunization. More importantly, collection of primary epidemiologic and economic data should be undertaken in parallel. Despite the existing gaps in data, further research using the most current data should facilitate decisions on new vaccination strategies by describing conditions for favorable results and quantifying the margin of uncertainty.

Pertussis immunization of adolescents in the United States: an economic evaluation

The incidence of reported pertussis has increased during the past decade and poses a growing health and economic burden in developed countries, despite high rates of primary vaccination. Administration of a booster dose of acellular pertussis vaccine to adolescents may help reduce this burden, not only by reducing infections in vaccinated individuals but also by reducing transmission of Bordetella pertussis to other individuals, particularly infants. An epidemiologic model was created to assess the health and economic impact of implementing a program of routine acellular pertussis immunization in adolescents 11-18 years of age in the United States, considering both the reduction in cases in those vaccinated and among the unvaccinated population (due to herd immunity). Inputs for the base case were defined according to information derived from published literature and were supplemented by estimates provided by members of the Global Pertussis Initiative. Both direct and indirect costs were included (in 2002 US dollars) using U.S. data. Outcomes were evaluated over the lifetime of a cohort of potential adolescent vaccine candidates. Because of uncertainty in many of the inputs, extensive sensitivity analyses were conducted. With 80% vaccination coverage of adolescents and a 20% reduction of other cases because of herd immunity, >68,000 cases and 41 pertussis-related deaths would be avoided in the subsequent 10 years by routine administration of acellular pertussis boosters to a single cohort of adolescents in the United States. This strategy would be cost-effective, incurring from 6000 US dollars to 22,000 US dollars per life-year gained. The level of herd immunity attained and the true incidence of pertussis are critical determinants of cost effectiveness, as is the duration of immunity resulting from immunization. The cost of immunization and the discount rate also play a role. Although there is considerable uncertainty surrounding key inputs, the results indicate that the conditions required for adolescent immunization to be economically warranted are realistic.

Pertussis vaccination strategies for neonates—an exploratory cost-effectiveness analysis

Hospitalisation and death from pertussis in highly immunised populations largely occurs before the first vaccination at 2 months. A Markov model was constructed to estimate the costs and health consequences of three strategies to reduce pertussis over the first 6 months of an infant's life. Earlier vaccination (at either birth or 1 month in addition to current practice) or vaccination of the parents soon after birth was compared with the current practice of vaccination at 2, 4 and 6 months. The model was populated using data on the incidence and costs from Australia. Disability-adjusted life-years (DALYs) were used as the primary outcome measure. The cost to the Australian public health system was chosen as the economic perspective, and Monte-Carlo simulations were used to accommodate uncertainties in the variables. Vaccination at birth was estimated to cost (S.D.) an additional A$33.21 (A$1.60) per infant and to reduce cases, deaths and DALYs by 45%. Vaccination at 1 month was estimated to cost an additional A$43.24 (A$8.98) per infant and to reduce morbidity by approximately 25%. Parental vaccination at birth was the most expensive alternative, costing an additional A$73.38 (A$4.98) per infant and reducing pertussis morbidity by 38%. The costs per DALY averted were A$330,175 (A$15,461) A$735,994 (A$147,679) and A$787,504 (A$48,075) for the birth, 1 month and parental vaccination strategies, respectively. Changing the estimated factor by which hospitalisations and deaths are under-reported, and the efficacy of early vaccination, had large effects on results. Parental vaccination at birth was most cost-effective where protection persisted for subsequent children. The birth vaccination strategy appears to offer the greatest potential benefit for one-child families, but the efficacy at birth (and 1 month) needs to be established.

Which strategy for pertussis vaccination today?

Pertussis (whooping cough) remains an epidemic disease responsible for infant and child morbidity and mortality, and is perceived as a serious public health problem. Since the widespread use of whole-cell pertussis vaccines in the 1940s, vaccination programs have varied greatly between countries. National specificity is a function of several factors. The most important are: vaccine efficacy and tolerability;vaccine coverage and distribution; and vaccine acceptance by parents and professionals. During the 1970s, Sweden, England, Wales and Japan provided contrasting examples of the attitude of health authorities to the use of whole-cell vaccines. The increase in pertussis incidence was noted as a consequence of active opposition to this vaccine. The re-emergence of pertussis in the 1990s, in countries with high vaccination coverage and increased incidence of disease in individuals >15 years and <6 months of age, has drawn attention to the role of booster doses of pertussis vaccines and their introduction into regular vaccination programs. The use of acellular vaccines for booster doses for adolescents and adults would seem unambiguous because of their decreased reactogenicity, although the exact schedule has yet to be established. The choice between the two kinds of vaccines is more difficult for primary courses, where safety and efficacy profiles are similar, and the attitude towards acellular vaccines varies from country to country. In this case, the strategy adopted results from the national history of pertussis infection and from the quality of the available whole-cell vaccine. Two contrasting examples are the US, where acellular vaccines were licensed for the primary series in the 1990s, and the UK, where whole-cell vaccines are exclusively used for primary immunization. The changing epidemiology of pertussis, and its local diversification, would suggest that at present it is difficult to define a single worldwide strategy with only one kind of vaccine and one schedule. In order to control pertussis incidence, each country should continue to determine the best national vaccination program established in very close relation to the past and present epidemiological situation and available healthcare resources.

The potential cost-effectiveness of acellular pertussis booster vaccination in England and Wales

A cost-effectiveness analysis of the introduction of acellular pertussis booster doses at either 4 or 15 years of age was performed. A transmission dynamic model was used to predict the level of indirect protection in those too young to be vaccinated. Multivariate sensitivity analyses were performed. In England and Wales there are an estimated 35,000 general practitioner (GP) consultations, 5500 inpatient days, and nine deaths annually attributable to pertussis, despite high levels of coverage for the primary course (approximately 95%). Around 80% of the bed-days and 90% of the deaths occur in those too young to be immunised (< 3 months of age). The introduction of acellular booster doses at 4 years is expected to reduce morbidity and mortality in the younger age groups by 40-100%, and at 15 years by 0-100%. From the perspective of the health care provider, roughly 50% of the simulations result in a cost per life-year gained of less than 10,000 pounds for vaccination at 4 years, the corresponding proportion for vaccination at 15 years being only 35%. Apart from the degree of indirect protection the model was most sensitive to the discount rate, the price of the vaccine, and the mortality rate. Significant uncertainty remains regarding the epidemiology of pertussis and the impact of booster doses. Nevertheless, the introduction of acellular boosters, particularly at 4 years, has the potential to be cost-effective in the UK.

How do Italian pharmacoeconomists evaluate indirect costs?

OBJECTIVES

To investigate how indirect costs are evaluated in pharmacoeconomic studies in Italy and the attitude of Italian pharmacoeconomists toward indirect costs.

METHODS

A literature review was conducted, specifically focused on pharmacoeconomic studies including indirect costs carried out in Italy, and a suevey among Italian pharmacoeconomics experts.

RESULTS

Nineteen studies were available for review. Although the methods used to calculate the value of production loss due to morbidity were all based on the Human Capital Approach (HCA), there was a wide variability among studies in practical methods. The parameters used to value production losses varied widely too. Of the 25 survey responders, 20 considered it important to include indirect costs in pharmacoeconomic studies; 56% of those interviewed stated that health authorities should require indirect cost evaluations. Most of these experts would include indirect cost estimates in drug-pricing calculation.

CONCLUSIONS

In Italy studies evaluating indirect costs are still only few, although there is evidence of an increase. Italian pharmacoeconomists are far from reaching any consensus on methods for evaluating these costs. Methods need to be standardized particularly with respect to the parameters used to quantify productive time lost in monetary terms.

Mothers as active partners in the prevention of childhood diseases: maternal factors related to immunization status of preschool children in Italy

BACKGROUND

We examined how maternal socio-demographic factors, together with mother's education, knowledge, and perception of immunizations, can affect the uptake of optional vaccinations of preschool children in Italy.

METHODS

Interviews of Italian mothers were performed using a structured questionnaire administered by trained interviewers with no specific medical competence.

RESULTS

A convenience sample of 1,035 mothers were interviewed. Fifty-nine percent of the respondents reported to have had their child immunized with the MMR vaccine and 54% reported to have had their child immunized against pertussis. In logistic regression analysis, three variables were significantly associated with both the immunization outcomes: mother's positive attitude toward immunization (OR = 1.69; IC 1.13-2.52 for pertussis; OR = 1.86, IC 1. 17-2.96 for MMR); mothers' residency in the North of the country (OR = 1.74; IC 1.32-2.30 for pertussis; OR = 1.63, IC 1.18-2.24 for MMR); and mother's receipt of satisfactory information on immunization (OR = 1.67; IC 1.15-2.21 for pertussis; OR = 2.25, IC 1. 47-3.43 for MMR). An immunization performed in recent years (after 1994), probably following the widespread use of acellular vaccine, was the most significant predictor for pertussis immunization (OR = 3.21; IC 2.43-4.24).

CONCLUSIONS

The findings suggest that mothers' attitudes, educational level, and socio-demographic characteristics, as well as socio-economic factors and local health policies, can influence children's immunization uptake. Health promotion, based on a partnership between parents and health professionals, should become a priority in Italian vaccination policies.