Encouraging demand for new and increasingly cheap interventions available now can boost health in developing countries, says Charles Kenny.
The conventional wisdom is that wealthier is healthier: staying alive longer takes expensive stuff, and so a country's quickest way to better health for its people is economic development.
There's a lot to that argument. Good nutrition, shelter, hospitals — they all cost money. And that's surely a big part of why life expectancies in high-income countries are twenty years longer than those in low-income countries worldwide, according to World Bank data. Even within countries, household surveys suggest richer families live longer and stay healthier than poorer ones.
But the good news is that income is only one factor, and not the most important one, in explaining global health outcomes. It doesn't take a lot of money to sustain a long and healthy life even in the poorest countries. The challenge is to ensure that a cheap basic package of health interventions is available to — and is used by — all.
Ever more affordable
Survey data suggest that basic primary health services can be delivered in rural areas at very low cost — US$2.82 per person in Cambodia, for example, and US$6.25 in Guatemala. 
Cheap interventions like vaccination, better hygiene, bednets, oral rehydration, breast feeding, antimalarial drugs and antibiotics can prevent or ameliorate the big child killers in developing countries — communicable diseases like measles and malaria as well as sepsis and diarrhoea.
Even better, cost has been dropping over time as simple, more cost-effective approaches are being rolled out. For example, a sugar, salt and water mix for oral rehydration can prevent most deaths from diarrhoea and can be administered by anyone. This simple treatment has largely replaced the earlier intravenous saline solution that had to be administered by a nurse.
More recently, in the last couple of years, donor agencies and developing country governments have begun rolling out the first vaccine against pneumococcal disease strains common in developing countries. This vaccine, against the leading global killer of children under the age of five, costs just US$3.50 a dose.
The low cost of these interventions means they could be distributed quickly even in some of the poorest and most remote areas of the world. For example, between 1974 and 2000, the level of immunisation against six diseases — measles, diphtheria, pertussis, tetanus, tuberculosis and polio — increased from five to 80 per cent of the world's newborns.
As a result of expanded vaccination coverage, the number of measles cases worldwide reported to the WHO fell from 4.5 million in the early 1980s to below 400,000 by 2010.
That is why even very poor countries are seeing dramatic improvements in health outcomes. My colleague Ursula Casabonne and I recently estimated that child mortality for a country with an income of $1,000 per capita was 22.4 per cent in 1975, but that had dropped to 16.3 per cent by 2005.
This is part of a global trend towards improved health outcomes first detected by Samuel Preston thirty-five years ago.  Preston found that, while richer countries remained healthier than poorer countries, countries at the same level of income over time were seeing dramatically better health outcomes.
The rollout of simple and cheap interventions helps to explain the weak link between rates of health improvement and the rate of economic growth across countries — and so the importance of factors other than wealth. It also accounts for the rapid improvement in global health, despite a declining number of hospital beds per person worldwide.
But better health also requires changes on the demand side — and this is perhaps most underappreciated by the development community. It requires parents who breast feed; get their kids vaccinated; put them under bednets; demand their kids use soap (and use it themselves); and use oral rehydration to treat diarrhoea.
Survey data from 45 low-income countries show that the prevalence of common diseases had little power in explaining whether a particular child lived or died. But educating parents to seek the right treatment could lower child mortality by nearly a third. 
This suggests that development agencies and policymakers should be spending more time exploring ways to improve uptake of health practices and innovations.
Many simple interventions on the demand side of health show promise. For example, providing a bag of lentils to parents who get their kids vaccinated improves vaccination rates considerably. And carefully designed community-based learning for pregnant mothers about birth preparedness, clean deliveries, breastfeeding and how to recognise danger signs can significantly reduce neonatal deaths.
Health systems in developing countries need to improve — but that is only part of the battle. Better health need not wait on economic development. And neither does it require an extensive network of hospitals staffed with doctors.
What it does require is widespread access to basic health tools and services, not least vaccination programmes, skilled birth attendants, and clinics stocked with antimalarials and basic antibiotics. Developing new, cheap interventions, and boosting demand for them, is a vital part of reducing mortality across the world.
Charles Kenny is a senior fellow at the Center for Global Development in Washington DC. He is author of Getting Better: Why Global Development is Succeeding (Basic Books, 2011) and, with Ursula Casabonne The Best Things in Life are Nearly Free: Technology, Knowledge and Global Health (forthcoming in World Development).
 Loevinsohn,B and Harding, A. Buying results? Contracting for health service delivery in developing countries. The Lancet: 676–681 (2005)
 Preston, S. H. Causes and Consequences of Mortality Declines in Less Developed Countries during the Twentieth Century [1MB]. In Population and Economic Change in Developing Countries (Ed. Easterlin, R.A.). University of Chicago Press (1980)
 Boone P. and Zhan Z. Lowering Child Mortality in Poor Countries: The Power of Knowledgeable Parents [705kB]. (2006)