Because of the vaccine alliance Gavi, U.N. agencies, the World Bank, the Bill & Melinda Gates Foundation and other donors, immunizations have soared in developing countries over the past 15 years. As a result, an estimated 7 million children have survived infancy who before the year 2000 would have died young.

But vaccine schedules are increasingly complex, and young mothers often forget to take children in for shots on time.

A clever solution occurred to Lauren Braun, a former Cornell pre-med student, when she spent a summer working in Peru, traveling to villages to remind mothers to take children to clinics for immunizations.

Her nonprofit company, Alma Sana, makes flexible silicon bracelets, like the yellow Livestrong bands so popular a decade ago. But hers come in pink or blue, fit around a newborn’s ankle, and serve as tiny calendars.

For example, beneath the number 4 on the bracelet - 4 months old - are a triangle, a circle, an X and a square. They represent the vaccines against polio, pneumonia and rotavirus, as well as the pentavalent shot, which protects against five diseases.

As the baby receives each one, a nurse uses a hole punch to puncture the appropriate mark. When every mark on the bracelet is punched, the baby is fully protected.