Each year, preventable diseases like malaria and dengue cause the deaths of 700,000 people. Intestinal worm infections affect an estimated 1.5 billion people, mostly in poor communities. Left alone, these diseases also take a massive economic toll, costing low- and middle-income countries billions of dollars each year through healthcare costs, lost productivity, and missed opportunities for education and economic growth. What do mosquito nets, deworming pills, and water treatment products have in common? They are examples of cheap, proven tools that protect people from these common preventable diseases, especially in low- and middle-income countries.

When people use these preventive products, they’re less likely to get sick from preventable illnesses. That means kids miss less school, adults miss less work, and families are healthier. But the impact doesn’t stop there. Because many illnesses are contagious, if these products are widely used in a community, it can stop disease outbreaks before they start, keeping others in the community healthy too.

Some might assume that charging a fee for these products ensures they reach people who value and plan to use them—or that paying a fee makes people want to use the products more. But research tells a different story. Evidence from seventeen studies shows that even low prices can discourage families in need from accessing them, actually reducing the reach and effectiveness of these products. Several studies also show that design tweaks, like offering free vouchers, can lower cost without reducing impact by making sure families who are motivated to use a product can access it.

The policy takeaway is clear: Policymakers and healthcare providers should eliminate user fees and distribute cheap but effective preventive health products for free. Offering them for free makes it far more likely that people actually get and use them, benefiting themselves and others.