Helen Keller International
Rees Calder · 28 April 2026 · 7 min read
Vitamin A deficiency kills children in a way that's almost invisible. It weakens immune systems, making ordinary infections lethal. It causes blindness. It stunts growth. And it affects roughly 190 million children under five worldwide, almost entirely in sub-Saharan Africa and South Asia (WHO, 2024). The solution has existed for decades: a single high-dose vitamin A capsule, given twice a year, that costs roughly $1-2 per child to deliver.
Helen Keller International (HKI) has been delivering vitamin A supplementation at scale since the 1990s. GiveWell added them to their top charity list in 2021, and by 2024 they were receiving over $40 million in GiveWell-directed funding annually. The programme operates in over 20 countries and reaches tens of millions of children each year.
The evidence
The evidence for vitamin A supplementation is among the strongest in global health.
The Cochrane review. The gold standard systematic review (Imdad et al., updated 2022) analysed 47 randomised controlled trials involving over 1.3 million children across 19 countries. The headline finding: vitamin A supplementation reduces all-cause mortality in children aged 6 months to 5 years by roughly 24% (relative risk 0.76, 95% CI 0.69-0.83). That's not a small effect. One in four preventable deaths in this age group, eliminated by a capsule that costs pennies.
Why 24% seems implausibly large. It's not reducing deaths from vitamin A deficiency specifically. It's reducing deaths from everything, because vitamin A is critical for immune function. Children with adequate vitamin A fight off measles, diarrhoea, and respiratory infections more effectively. The capsule doesn't treat any single disease; it makes the child's immune system competent enough to survive the ordinary diseases of childhood in low-resource settings.
The mechanism. Vitamin A maintains epithelial tissues (the lining of the gut, lungs, and eyes) and supports T-cell function. Deficient children have compromised mucosal barriers and weakened cellular immunity. A high-dose capsule (200,000 IU for children over 12 months, 100,000 IU for 6-12 months) restores adequate levels for roughly 4-6 months. Hence twice-yearly supplementation.
How HKI delivers
Helen Keller International's vitamin A supplementation programme uses a mass campaign model rather than a clinic-based model.
Campaign days. HKI coordinates with national governments to run semi-annual "Child Health Days" or "Vitamin A Supplementation Days." On designated dates, health workers and community volunteers fan out across districts, setting up distribution points at health clinics, schools, markets, and community centres. The goal is to reach every child aged 6-59 months in the target area within a few days.
Coverage rates. HKI's programme data shows coverage rates of 80-95% in their operating areas, which is remarkably high for a health intervention in low-resource settings. The campaign model works because it concentrates resources, creates community awareness, and removes the need for individual families to seek out services.
Cost structure. The capsules themselves cost roughly $0.02-0.05 each. The vast majority of the cost is delivery: paying community health workers, training, logistics, supervision, and monitoring. HKI's total cost per child supplemented is roughly $1-2, depending on the country and the density of the population.
Integration. Many campaign days combine vitamin A with deworming treatment, which is cheap to add (roughly $0.20-0.50 per child) and addresses a complementary health problem. HKI often partners with other organisations to deliver both interventions simultaneously, improving cost-effectiveness for both.
Cost-effectiveness
GiveWell's 2024 cost-effectiveness analysis places Helen Keller International's vitamin A supplementation at roughly 8-12x the impact per dollar compared to unconditional cash transfers (GiveDirectly). This makes it one of the most cost-effective health interventions in GiveWell's portfolio.
How GiveWell calculates this. The model combines: the mortality reduction from the Cochrane review (24%), the baseline mortality rate in HKI's operating areas, the programme's coverage rate, the cost per child reached, and adjustments for uncertainty. GiveWell applies significant downward adjustments for internal validity concerns, external validity (generalising trial results to HKI's specific contexts), and the possibility that the Cochrane estimate overstates the true effect. Even after these adjustments, vitamin A supplementation remains highly cost-effective.
The "too good to be true" question. Some researchers have questioned whether the 24% mortality reduction still holds in 2024, given that baseline child mortality has declined significantly since the original trials (mostly conducted in the 1980s and 1990s). If fewer children are dying from infections overall, the absolute benefit of vitamin A may be smaller. GiveWell accounts for this by using current mortality rates rather than historical ones, and the programme still clears their cost-effectiveness bar by a wide margin. A recent large RCT in India (DEVTA trial, Awasthi et al., Lancet 2013) found a smaller effect (4% mortality reduction, not statistically significant), which GiveWell incorporates as a downward adjustment. The overall estimate remains strongly positive.
Where HKI operates
Helen Keller International runs vitamin A supplementation programmes in over 20 countries, concentrated in:
West Africa: Burkina Faso, Cameroon, Cote d'Ivoire, Guinea, Mali, Niger, Senegal, Sierra Leone. These are among the highest-burden countries for vitamin A deficiency globally.
East and Southern Africa: Kenya, Madagascar, Mozambique, Tanzania. Madagascar has some of the highest deficiency rates in the world.
Southeast Asia: Cambodia, Indonesia, Nepal. Deficiency rates are lower than in Africa but still significant.
The geographic spread matters because it diversifies risk. Political instability, natural disasters, or health system disruptions in any single country don't shut down the entire programme.
What makes HKI distinctive
Among GiveWell's top charities, HKI has several unusual features.
Leverage on government systems. HKI doesn't run a parallel health system. They provide technical assistance, funding, and monitoring to help governments deliver vitamin A through their existing health infrastructure. This means HKI's cost per child includes only the marginal cost of supplementation, not the full cost of the health system. It also means the programme is more sustainable: if HKI withdrew, the government systems would still exist.
Monitoring quality. HKI conducts independent coverage surveys after each campaign round, using representative household samples to verify that children actually received the capsule. This is unusual in the supplementation space, where many programmes rely on administrative data (which tends to overcount). GiveWell has repeatedly cited HKI's monitoring as a reason for higher confidence in their impact estimates.
Room for more funding. GiveWell's 2024 analysis identified substantial room for HKI to expand, particularly in countries where they have government partnerships but insufficient funding to reach all eligible children. This is one of the reasons GiveWell has directed significant funding to HKI in recent years.
The fortification alternative
Vitamin A supplementation is a "vertical" intervention: a targeted programme delivering one specific nutrient. The alternative approach is "horizontal" fortification: adding vitamin A to staple foods (cooking oil, sugar, flour) that the entire population already consumes.
The case for fortification. It reaches everyone, including adults. It doesn't require campaign infrastructure. Once established, it's self-sustaining through the food supply chain. The Global Alliance for Improved Nutrition (GAIN) and the Food Fortification Initiative have championed this approach.
The case for supplementation. Fortification takes years to establish and depends on industrial food processing infrastructure that doesn't exist in many of HKI's operating areas. Young children may not consume enough fortified foods to reach adequate levels. And the evidence base for supplementation's mortality impact is much stronger than for fortification.
The pragmatic view. Both approaches are needed. Fortification is the long-term solution. Supplementation is the bridge that saves lives while fortification infrastructure develops. HKI operates in the space where that bridge is most needed.
For your giving
Helen Keller International accepts donations directly and through GiveWell's Maximum Impact Fund.
The case for HKI specifically: If you want to fund one of the most evidence-backed health interventions in existence, with 47 RCTs behind it and a 24% mortality reduction, HKI is hard to beat on sheer strength of evidence.
The case for Maximum Impact Fund: If you trust GiveWell's marginal allocation. In any given quarter, GiveWell may direct more funding to malaria charities or New Incentives if they judge those have higher marginal impact at that moment.
A note on moral intuition: Vitamin A supplementation has a clarity that some people find compelling. A capsule that costs $1-2, given to a child twice a year, that reduces their chance of dying by roughly a quarter. The directness of the intervention, the strength of the evidence, and the scale of the need make it a powerful example of what effective giving can look like.
One sentence
Helen Keller International delivers vitamin A capsules to tens of millions of children across 20+ countries at roughly $1-2 per child, backed by 47 RCTs showing a 24% reduction in child mortality, making it one of the most cost-effective and evidence-supported charities in existence.
Sources used: GiveWell Helen Keller International charity page and cost-effectiveness analysis (2024), Imdad et al. Cochrane systematic review of vitamin A supplementation (updated 2022, 47 RCTs, 1.3 million children), Awasthi et al. DEVTA trial (Lancet, 2013), WHO vitamin A deficiency global prevalence estimates (2024), Helen Keller International annual report and programme data (2024), GiveWell Maximum Impact Fund allocation methodology (2024), Global Alliance for Improved Nutrition fortification evidence (2024). Full links in the planning doc.