As President Biden convenes heads of state for a Covid-19 summit on Wednesday, pressure is growing on American drug companies — particularly Moderna, the upstart biotech firm that developed its coronavirus vaccine with billions of dollars in taxpayer money — to share their formulas with manufacturers in nations that desperately need more shots.

Last year’s successful race to develop vaccines in extraordinarily short order put companies like Moderna and Pfizer in a highly favorable spotlight. But now, with less than 10 percent of those in many poor nations fully vaccinated and a dearth of doses contributing to millions of deaths, health officials in the United States and abroad are pressing the companies to do more to address the global shortage.

The Biden administration has privately urged both Pfizer and Moderna to enter into joint ventures where they would license their technology to contract manufacturers with the aim of providing vaccines to low- and middle-income countries, according to a senior administration official.