"More than a million cases of meningitis have been reported in Africa over the past two decades, and the vaccine works against the group A meningitis strain that causes more than 8 out of 10 cases on the continent. Moreover, it costs less than 50 cents a dose. In the United States, Novartis and Sanofi Pasteur market a single dose of meningitis vaccines against multiple strains of the disease for $80 to $100.

“Wow, that’s remarkable!” exclaimed Dr. Gregory A. Poland, head of vaccine research at the Mayo Clinic in Minnesota, when he heard how little the new vaccine would cost.

Bill Gates, whose foundation largely financed the endeavor, contrasted the undertaking with the development of vaccines for measles, smallpox and polio.

“All those things were created because rich people got sick,” he said in an interview. “This is the first vaccine that went through the whole process where there was no rich world market, and it had to be optimized at a very low price.”