(CNN) Pfizer and Moderna are testing their coronavirus vaccines to see if they work against the mutated version of the virus found in the United Kingdom and other countries, the companies said. US has not restricted UK travelersThe novel coronavirus has mutated before, and both companies' vaccines worked against variations of the virus. JUST WATCHED Watch Joe Biden receive coronavirus vaccine Replay More Videos ... MUST WATCH Watch Joe Biden receive coronavirus vaccine 01:51The outbreaks are not confined to one region. Researchers are trying to determine if the UK variant is more transmissible, but Fauci said it doesn't appear more deadly. Some researchers examining the UK variant have concerns the mutations might diminish the vaccines' effectiveness.

Source: CNN December 22, 2020 07:18 UTC