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Both appear to be more than 90 percent effective in clinical trials and could begin to be available before the end of the year.
The vaccines are made by different companies: One is being developed by pharmaceutical giant Pfizer and its German partner, BioNTech, and the other by biotechnology firm Moderna, in partnership with the National Institute of Allergy and Infectious Diseases. Both drugmakers have moved at record speed and will seek regulatory clearance for their vaccines in the coming weeks.