4 Min Read MEXICO CITY (Reuters) - The U.S. government is expected to respond by Friday to Mexico’s request to share doses of stockpiled AstraZeneca COVID-19 vaccines, a senior Mexican official said Tuesday, as Canadian authorities also seek extra doses from their southern neighbor. Airline employees unload a container with a batch of the AstraZeneca's COVID-19 vaccine, at the Benito Juarez International Airport, in Mexico City, Mexico March 16, 2021. Mexico Presidency/Handout via REUTERS Reuters reported this week that Mexico had asked for extra shipments of the British-developed vaccine, since it has yet to be approved for use in the United States.