The fast-spreading Omicron coronavirus variant recently identified in South Africa has virologists and health authorities on edge because of its many mutations, but much about its infectiousness and virulence remains unknown.

Scientists said some of the roughly 50 mutations on the new variant, called B.1.1.529, could potentially render it more transmissible or reduce vaccine effectiveness. But it will take time for virologists and infectious-disease researchers to study the variant’s spread and the potential impact on vaccines and therapeutics.