CARACAS, June 24 (Reuters) - Venezuela received its first shipment of doses of leftist ally Cuba"s Abdala coronavirus vaccine on Thursday, the South American country"s vice president said, while slamming wealthy countries for "sabotaging" the COVAX vaccine-sharing scheme. Authorities did not specify how many doses had arrived from Cuba, but did say that Venezuela had signed a contract to purchase 12 million doses of the shot. Cuba said earlier this week that the three-shot Abdala vaccine had proved 92.28% effective in last-stage clinical trials. read more "This is true international cooperation, the brotherhood and friendship that we must demonstrate and be an example for other governments," Vice President Delcy Rodriguez said in a state television address. Venezuela since February has received some 3.5 million doses of Russian and Chinese vaccines for its population of some 28 million. Doctors and vaccine recipients have criticized the socialist government"s vaccination rollout as slow and confusing. read more The once-prosperous OPEC nation is mired in a multi-year economic collapse that has left its healthcare system short of resources and with unreliable electricity and water supply. President Nicolas Maduro"s government and allies like Cuba blame U.S. sanctions for the economic woes, though critics say the unraveling of Venezuela"s socialist model is the root cause. President Nicolas Maduro"s government in April said it had paid the COVAX initiative, intended to facilitate vaccine access to poor countries, for 5 million doses, which have not yet arrived. Officials said earlier this month that four of its payments had been "blocked." "Rich countries have sabotaged this solidarity mechanism to distribute vaccines to the world," Rodriguez said. "Rich countries try to use the vaccines as an instrument of political blackmail." Her comments came after Reuters reported on Wednesday that COVAX, co-led by the World Health Organization (WHO) was planning a reorganization to prioritize poor countries, citing internal WHO documents. read more