The UK has eased restrictions on COVID-19 prevention and control, but for the first time since January, more than 50,000 confirmed cases have been reported in a single day, prompting worries over another lockdown. So are vaccines effective? Can vaccination really create the herd immunity people expect? Tian Wei talked to Dr. Belén Garijo, the chairwoman of the Executive Board and CEO of Merck, one of the world's largest pharmaceutical companies, and also a key supplier of raw materials for COVID-19 vaccines.

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