Modeling the cost-effectiveness of maternal acellular pertussis immunization (aP) in different socioeconomic settings: A dynamic transmission model of pertussis in three Brazilian states

Equity in Economic Evaluations of Early Childhood Development Interventions in Low-and Middle-Income Countries: Scoping Review

OBJECTIVES

This study aimed to examine how equity is integrated into economic evaluations of early childhood development interventions in low-and middle-income countries (LMICs), and to narratively synthesize the study characteristics and findings.

METHODS

We conducted a scoping review by searching three electronic databases with terms including equity, early childhood development intervention, economic evaluation, and LMICs. Interventions that aimed to improve child cognitive, physical, language, motor, or social and emotional development through health, nutrition, security and safety, responsive caregiving, and early learning interventions between conception and age 8 years were considered. Studies published in English peer-reviewed journals in the year 2000 and later were included.

RESULTS

The review included 24 cost-effectiveness studies out of 1460 identified articles based on eligibility criteria. The included studies addressed health, nutrition, social protection, and water, sanitation and hygiene interventions for child development. The common type of intervention was immunization. Mostly, equity was measured using household wealth or geographic areas, and the study findings were presented through subgroup analyses. The study settings were LMICs, but most studies were conducted by research teams from high-income countries. Overall, 63% of included studies reported that early childhood development interventions improved equity with greater intervention benefits observed in disadvantaged groups.

CONCLUSIONS

Consideration of equity in evaluations of early childhood interventions provides a more complete picture of cost-effectiveness, and can improve equity. Greater focus on promoting equity consideration, multi-sectoral interventions, and researchers in LMICs would support evidence-based interventions and policies to achieve equity in child development.

Cost-effectiveness of maternal pertussis immunization: Implications of a dynamic transmission model for low- and middle-income countries

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(84) Low- and middle-income countries (LMICs) have experienced a resurgence of pertussis.

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(74) Maternal aP immunization could prevent pertussis among very young infants.

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(84) A dynamic transmission model was used to evaluate maternal aP immunization in LMICs.

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(82) Maternal aP is cost-effective when infant vaccination coverage is moderate or low.

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(85) Maternal aP immunization is not cost-effective in LMICs with infant coverage 90-95%.

Objective

This study evaluates the cost-effectiveness of maternal acellular pertussis (aP) immunization in low- and middle-income countries using a dynamic transmission model.

Methods

We developed a dynamic transmission model to simulate the impact of infant vaccination with whole-cell pertussis (wP) vaccine with and without maternal aP immunization. The model was calibrated to Brazilian surveillance data and then used to project health outcomes and costs under alternative strategies in Brazil, and, after adjusting model parameter values to reflect their conditions, in Nigeria and Bangladesh. The primary measure of cost-effectiveness is incremental cost (2014 USD) per disability-adjusted life-year (DALY).

Results

The dynamic model shows that maternal aP immunization would be cost-effective in Brazil, a middle-income country, under the base-case assumptions, but would be very expensive at infant vaccination coverage in and above the threshold range necessary to eliminate the disease (90–95%). At 2007 infant coverage (DTP1 90%, DTP3 61% at 1 year of age), maternal immunization would cost < $4,000 per DALY averted. At high infant coverage, such as Brazil in 1996 (DTP1 94%, DTP3 74% at 1 year), cost/DALY increases to $1.27 million. When the model’s time horizon was extended from 2030 to 2100, cost/DALY increased under both infant coverage levels, but more steeply with high coverage. The results were moderately sensitive to discount rate, maternal vaccine price, and maternal aP coverage and were robust using the 100 best-fitting parameter sets. Scenarios representing low-income countries showed that maternal aP immunization could be cost-saving in countries with low infant coverage, such as Nigeria, but very expensive in countries, such as Bangladesh, with high infant coverage.

Conclusion

A dynamic model, which captures the herd immunity benefits of pertussis vaccination, shows that, in low- and middle-income countries, maternal aP immunization is cost-effective when infant vaccination coverage is moderate, even cost-saving when it is low, but not cost-effective when coverage levels pass 90–95%.

Comparison of static and dynamic models of maternal immunization to prevent infant pertussis in Brazil

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Dynamic transmission models of infectious disease capture the herd immunity effects of vaccination.

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We compared dynamic and static models of maternal acellular pertussis (aP) immunization built with Brazilian data.

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At infant vaccine coverage < 90–95%, both models estimate that maternal immunization is cost-effective.

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Only the dynamic model shows that maternal immunization is not cost-effective at infant coverage > 90–95%.

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The background effect of routine infant vaccination is critical to the cost-effectiveness of maternal aP immunization.

Background

This paper compares cost-effectiveness results from two models of maternal immunization to prevent pertussis in infants in Brazil, one static, one dynamic, to explore when static models are adequate for public health decisions and when the extra effort required by dynamic models is worthwhile.

Methods

We defined two scenarios to explore key differences between static and dynamic models, herd immunity and time horizon. Scenario 1 evaluates the incremental cost/DALY of maternal acellular pertussis (aP) immunization as routine infant vaccination coverage ranges from low/moderate up to, and above, the threshold at which herd immunity begins to eliminate pertussis. Scenario 2 compares cost-effectiveness estimates over the models’ different time horizons. Maternal vaccine prices of $9.55/dose (base case) and $1/dose were evaluated.

Results

The dynamic model shows that maternal immunization could be cost-saving as well as life-saving at low levels of infant vaccination coverage. When infant coverage reaches the threshold range (90–95%), it is expensive: the dynamic model estimates that maternal immunization costs $2 million/DALY at infant coverage > 95% and maternal vaccine price of $9.55/dose; at $1/dose, cost/DALY is $200,000. By contrast, the static model estimates costs/DALY only modestly higher at high than at low infant coverage. When the models’ estimates over their different time horizons are compared at infant coverage < 90–95%, their projections fall in the same range.

Conclusions

Static models may serve to explore an intervention’s cost-effectiveness against infectious disease: the direction and principal drivers of change were the same in both models. When, however, an intervention too small to have significant herd immunity effects itself, such as maternal aP immunization, takes place against a background of vaccination in the rest of the population, a dynamic model is crucial to accurate estimates of cost-effectiveness. This finding is particularly important in the context of widely varying routine infant vaccination rates globally.

Clinical Trial registry

Clinical Trial registry name and registration number: Not applicable.

Evaluating the cost-effectiveness of maternal pertussis immunization in low- and middle-income countries: A review of lessons learnt

This issue of Vaccine is devoted to papers from a research project that developed two types of simulation models, static and dynamic transmission, to evaluate the cost-effectiveness of maternal immunization to prevent pertussis in infants in low- and middle-income countries (LMICs). The research was conducted by a multinational team of investigators and funded by the Bill & Melinda Gates Foundation to gain an understanding of when and where maternal immunization might be a good public health investment for LMICs. Here we review the project's central lessons for vaccine policy and research. Models require a lot of data. As most LMICs lack good data, the models were built using pertussis disease burden data from Brazil, a middle-income country with three long-established, independent information systems (disease surveillance, hospitalization, and mortality), on the hypothesis that the disease process is similar across countries. Values for key parameters, particularly infant mortality, infant vaccine coverage, and costs of vaccination and treatment, were then varied to represent other LMICs. The results show that coverage levels of infant whole cell pertussis (wP) vaccine are key to the cost-effectiveness of maternal pertussis immunization. In settings where infant wP coverage is below the threshold thought necessary to eliminate pertussis in the population, 90-95%, maternal immunization is cost-effective, even cost-saving. By contrast, it is very expensive in countries capable of maintaining infant vaccination in or above the threshold range. The research also suggests that, while static models may serve to explore an intervention's cost-effectiveness initially, dynamic transmission models are essential for more accurate estimates. These findings can help guide policies toward maternal pertussis immunization, but also show that developing better data on neonatal pertussis mortality burden and infant vaccine coverage in LMICs, and on the duration of immunity of currently available pertussis vaccines, are key priorities to support better vaccine policy.