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Biden to ban travel from South Africa, reinstate restrictions on Brazil and U.K.
By Stephanie Beasley
EXPLAINER: Why it's hard to make vaccines and boost supplies
By Lauran Neergaard
Pfizer working on booster shot to protect against COVID-19 variants
By Dania Nadeem
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How scientists can 'copy and paste' Covid vaccines to work on the strain from South Africa
By Cory Stieg
Biden to impose travel restrictions on South Africa, U.K. and Brazil to mitigate new Covid strains
By Leslie Josephs & Emma Newburger