JOHANNESBURG—Dozens of nations restricted journey to and from South Africa and neighboring nations Friday, hoping to contain a quick-spreading new variant of the coronavirus that researchers say could be a lot more contagious and could render the recent crop of Covid-19 vaccines considerably less helpful.

Authorities from the Planet Health Group have been due to fulfill later on Friday to make your mind up no matter if to declare the new strain—currently recognized as B.1.1.529—a “variant of concern.” The WHO makes use of this label for virus strains that have been tested to be additional contagious, lead to much more significant health issues or decrease the usefulness of community-wellbeing measures, assessments, solutions or vaccines.