Where pharmaceutical companies have struck deals with partners, the pace of production has frequently disappointed.

“Even with voluntary licensing and technology transfer, it’s not easy to make complex vaccines,” said Dr. Krishna Udayakumar, director of the Duke Global Health Innovation Center.

Much of the global capacity for vaccine manufacturing is already being used to produce other lifesaving inoculations, he added.

But other health experts accuse major pharmaceutical companies of exaggerating the manufacturing challenges to protect their monopoly power, and implying that developing countries lack the acumen to master sophisticated techniques is “an offensive and a racist notion,” said Matthew Kavanagh, director of the Global Health Policy and Politics Initiative at Georgetown University.

With no clear path forward, Ms. Okonjo-Iweala, the W.T.O. director-general, expressed hope that the Indian and South African patent-waiver proposal can be a starting point for dialogue.

“I believe we can come to a pragmatic outcome,” she said. “The disparity is just too much.”

Peter S. Goodman reported from London, Apoorva Mandavilli from New York, Rebecca Robbins from Bellingham, Wash., and Matina Stevis-Gridneff from Brussels. Noah Weiland contributed reporting from New York.

View Source