"In our own small way, this is an opportunity for moms like me here in North America to help other mothers on a global level," Hayek, 41, said in a statement Wednesday.
Hayek's daughter, Valentina Paloma Pinault, was born in September.
The Pampers-UNICEF partnership has already provided more than 25 million vaccines to moms and babies in developing countries, where tetanus kills 140,000 infants and 30,000 women each year, according to UNICEF.