Interview with health economist, Dr Anushua Sinha, lead author of The Lancet paper

Dr. Anushua Sinha, MD, MPH, is Assistant Professor in the Department of Preventive Medicine & Community Health at the University of Medicine and Dentistry in New Jersey (UMDNJ). PneumoADIP had the opportunity to interview her on aspects of her recent Lancet publication analyzing the cost-effectiveness of pneumococcal conjugate vaccination in the prevention of child mortality. Lancet. 2007 Feb 3;369(9559):389-96.

What are the key findings of your study?

Pneumococcal vaccine saves lives, between 260, 000 and 470, 000 depending on the assumptions we used.

At cost per dose of between $1 and 5 it is a highly cost-effective health intervention, with a cost effectiveness ratio of between $22 and 100 per DALY averted.

Could you tell us, in lay terms, what sort of a model was used to estimate cost-effectiveness of pneumococcal conjugate vaccination in your study?

As clinicians and epidemiologists, our initial interest was in developing a model that captured as many aspects of pneumococcal disease epidemiology as possible - disease incidence, serotype distribution, mortality and morbidity, and health resource utilization. We quickly realized that with such a broad scope - our aim was to model 72 countries - and, frankly, with very little data available to populate the model, we were going to have to re-think this approach. We ended up building a model around the strengths of the data that actually were available to us for all 72 countries. That is, we built a "top-down" model, in which each child who is born in each of these 72 countries is at risk of dying before their fifth birthday. If a child is vaccinated, their risk of mortality is lower. Non-fatal pneumonia and meningitis may occur and may lead to hospitalizations. If a child is vaccinated, fewer cases of non-fatal pneumonia and meningitis occur. Child deaths and permanent disability result in disease burden. Costs are associated both with the vaccination program and with caring for disease. That's about it.

What are the underlying assumptions of the model? What are some of its strengths and limitations?

I think a basic assumption is that children in countries with higher child mortality rates are at greater risk of suffering death or disease that can be prevented by pneumococcal conjugate vaccine. That assumption is pretty well supported by recent disease burden models, vaccine trials and observational epidemiology. Another central assumption is that, within any given country, vaccine will reach the children who need it most. Finally, we assumed that the benefits and costs related to vaccine were those that we are accustomed to dealing with as clinicians and public health practitioners, ie benefits and costs related to the direct impact of vaccine on pneumococcal disease. We did not consider the impact on educational attainment, population growth, economic productivity beyond families of the vaccinees. Economists like David Bloom would argue that this understates vaccine's potential impacts.

We extrapolated from the Gambian trial of 9-valent vaccine for many of our vaccine-related model inputs. Obviously, the vaccine available right now is a 7-valent, with 10- and 13-valent products in the pipeline. So, we need to do some additional work to interpret the findings of this model in contexts where the 7-valent is being considered for introduction.

This model is meant to be complemented by country-level or regional work that better captures country-level or regional pneumocococcal disease burden, serotype distribution and estimates of avertable disease burden and avertable costs.

How do you foresee these findings translating to policy changes in the implementation of pneumococcal conjugate vaccine?

I think we've already seen an impact, in terms of the GAVI board approving the PneumoADIP investment case. My hope is that this work will contribute to the already growing understanding that a vaccine does not have to cost pennies a dose in order for it to provide value for money in developing world settings. As the understanding grows that newer vaccines - like pneumococcal conjugate vaccine - provide good investment value, the issues of affordability, sustainability and programmatic capacity are being addressed. Hopefully, this will all result in children who need the vaccine getting the vaccine.

Are there any future studies you wish to conduct based on these findings?

The short answer is yes. The one sentence answer is that the effect of regional variation of serotype distribution on these economic results, the impact of income discrepancies and vaccination rates on economic model results and the impact of indirect effects of vaccine (ie, herd immunity) on results are all important areas to investigate.

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