A vaccine for the coronavirus has proved 90% effective after early trials, according to its joint developers Pfizer and BioNTech. It’s raised hopes that the global coronavirus pandemic can be brought under control in the coming months – but as Henry Ridgwell reports, the nature of the vaccine means less developed health systems face major challenges in rolling out any inoculation programs.Camera: Henry Ridgwell    
Producer:  Henry Ridgwell, Mary Cieslak 
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