Tens of millions of Americans who work at companies with 100 or more employees will need to be vaccinated against COVID-19 by Jan. 4 or get tested for the virus weekly. The new requirements are the Biden administration’s boldest move yet to persuade reluctant Americans to finally get a vaccine that has been widely available for months — or potentially face financial consequences. If successful, administration officials believe it will go a long way toward ending a pandemic that has killed more than 750,000 Americans. The Occupational Safety and Health Administration says companies that fail to comply could face penalties of nearly $14,000 per violation. The requirements will apply to about 84 million workers at medium and large businesses.