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U.S. health officials warn delta Covid variant could cause fall surge in cases

04:05

As states across the country continue to lift remaining Covid-19 restrictions, health officials are warning that the delta variant, first detected in India, could cause a surge of Covid-19 cases in the fall. NBC News medical contributor, Dr. Natalie Azar, explains whether vaccines work against the variant and how long-term effects of the virus could impact a return to normalcy.