Billions of dollars have been spent in recent decades trying to prevent HIV transmission with pills, gels, vaccines and vaginal rings. So far, only two strategies have panned out: male circumcision and an expensive tablet taken daily.

Other than that, people are left to protect themselves with the humble condom. For far too many, it's all too humble.

When used correctly, the condom blocks HIV 95 percent of the time. Because it reduces sexual pleasure, however, it's often forsaken. The 2.5 million new HIV infections annually testify to that.

So, the Bill and Melinda Gates Foundation has set out to reinvent the device. It's offering $100,000 grants and a shot at $1 million in follow-up funding to people who can come up with good ways to improve the condom so that sex is at least as pleasurable with as without one.

It's a great idea. Sure, the condom has come a long way since 1564 when, according to the first recorded reference, linen versions were used in Italy, or since Japanese men wore tortoiseshell sheaths. Yet the device hasn't changed much since the invention of liquid latex in the 1930s. The modern mainstay is seamless, strong, thin, cheap, impermeable and has a long shelf-life. But latex doesn't conduct heat well, and even a fine layer reduces sensitivity.

The Gates foundation is already investing in a female condom spun from polymer micro-fibers, some of which would release a contraceptive while others emit an anti-HIV drug. This is an intriguing concept but almost certainly too expensive for sub-Saharan Africa, where 72 percent of new HIV infections occur.

Somewhat more realistic are products along the lines of the Origami condom, which is in advanced development by a California company. Because it's folded and slips on quickly, it addresses a significant reason why people decide not to use today's roll-on models: They're difficult to put on. Lubricated on the inside and shaped to produce friction, the Origami is designed to create for a man the sensation of condomless sex with a woman.

That feeling is especially important in situations, common in Africa, where women lack the status to persuade men to use condoms. A female condom, made by Female Health Company since 1993, addresses that issue but hasn't gained widespread acceptance because it's ungainly and relatively pricey. Research to produce more competitive female designs would help.

Improving the male version may be easier, however. By reaching out to experts in the rapidly advancing field of materials science, the foundation may find thinner alternatives to latex that preserve durability but increase heat transfer and allow for multiple features such as colors, scents and ridges -- in one device.

Grant approvers should be cognizant that donors now spend 2 to 4 cents each for the billions of condoms they distribute in Africa. At the same time, funders should begin to calculate how much more they could spend, cost-effectively, on improved models. A transformative innovation that made people prefer sex with a condom could be worth the investment. Marketed well, a popular condom could reduce the spread of HIV and thus the substantial costs of treating infections.

Have you got ideas how to improve the male or female condom and/or its packaging and marketing in the developing world? If so, please add a comment below.

(Lisa Beyer is a member of the Bloomberg View editorial board.)