"This will be the only such facility on the African continent," President Ruto said at an American Chamber of Commerce regional trade summit.
He said Moderna's investment "will be a catalyst for the medical and pharmaceutical industry not just in Kenya but in our continent".
Moderna said in a separate statement that the state-of-the-art facility would make up to 500 million doses of vaccines each year, without giving a date for when production would start.
"We hope to bring mRNA innovation to the people of Africa in areas of high unmet need, such as acute respiratory infections, as well as persistent infectious diseases like HIV and outbreak threats such as Zika and Ebola," said Moderna chief executive Stephane Bancel.
The company said it now has commitments to establish mRNA manufacturing facilities in Kenya, the United States, Canada, Australia, and the United Kingdom.
Moderna and other vaccine manufacturers hope that mRNA technology - which provokes an immune response by delivering genetic molecules containing the code for key parts of a pathogen into human cells - can accelerate immunisation development and production, and heighten efficacy.
Moderna to Build Nairobi Vaccine Plant
FILE: An airport worker stands next to boxes of Moderna coronavirus vaccine, donated by the U.S. government via the COVAX facility, after their arrival at the airport in Nairobi, Kenya on Aug. 23, 2021. Moderna announced building a Nairobi vaccine plant on March 30, 2023.
NAIROBI - US biotech company Moderna has finalized an agreement to set up a $500 million mRNA vaccine facility in Nairobi, Kenyan President William Ruto said Thursday.