REUTERS/Rodrigo GarridoNEW YORK, Sept 22 (Reuters) - The United States is significantly cutting back the number of Pfizer (PFE.N)/BioNTech (22UAy.DE) COVID-19 vaccine doses it will buy for donation to poorer nations this year, Pfizer said on Thursday, citing diminished demand for the shots in those countries. The United States will have an option to buy up to an additional 400 million shots for the program after this year. Pfizer said it had already delivered 400 million vaccine doses in 79 countries under the U.S. government contract. The vaccine doses were donated through the COVAX program, run by the World Health Organization and GAVI global vaccine alliance, which was intended to deliver COVID-19 shots to the world's poorer countries. COVAX has been negotiating since june with vaccine manufacturers to cut or slow deliveries of 400 million to 600 million vaccine doses from its own contracts.

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