COVID-19 updates: Michigan, Minnesota, New Mexico leading nation in cases

Austrian Chancellor Alexander Schallenberg announced Friday that the country will go into a full nationwide lockdown to curb a fourth wave of COVID-19 infections.

"We do not want a fifth wave," Schallenberg warned.

The lockdown will begin Monday and last for at least 10 days before the situation is reassessed. If the number of new COVID-19 cases has not dropped significantly, the lockdown can be extended to a maximum of 20 days.

Under the restrictions, people will be told to work from home, non-essential shops will close and public gatherings will be canceled. Schools will remain open for students who require in-person learning, but parents have been asked to keep their children at home if possible.

COVID-19 vaccination will also become mandatory by law in Austria, starting on Feb. 1.

It's the first country in Europe to make COVID-19 vaccines compulsory and the first to reimpose a full lockdown this winter, as the continent grapples with rising infections.

The Austrian government had initially imposed a nationwide lockdown only for the unvaccinated that began last Monday.

Mask-wearing cuts COVID-19 incidence by 53%, according to a new analysis that pooled results from multiple studies. 

The analysis, published Thursday in the medical journal The BMJ, found that mask-wearing, social distancing and hand-washing were all effective in reducing the spread of COVID-19.  

The bulk of the studies included in the analysis were conducted before mass vaccinations. The researchers, who were from several universities in Australia, Scotland and China, said that more studies are needed to understand the effectiveness of these public health measures in the context of widespread vaccination coverage.

-ABC News' Guy Davies, Esra Demirel and Sony Salzman

The Northeast and Midwest are seeing the largest jump in cases and hospitalizations, according to federal data.

Twenty-seven states have seen at least a 10% jump in daily cases over the last two weeks: Arizona, Arkansas, Connecticut, Delaware, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Mexico, New York, New York City, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Dakota, Tennessee, Utah, Vermont and Wisconsin.

Eighteen states have seen at least a 10% increase in hospital admissions over the last week: Georgia, Hawaii, Illinois, Indiana, Kentucky, Maine, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New Jersey, New Mexico, New York, Ohio, South Dakota, Texas and Wisconsin.

-ABC News' Arielle Mitropoulos

Florida Gov. Ron DeSantis on Thursday signed legislation that prohibits private employer vaccine mandates and says employers that violate the ruling will be fined.

The legislation also states educational institutions can't require students to be vaccinated; school districts can't have face mask policies or quarantine healthy students; and families can "sue violating school districts."

"Nobody should lose their job due to heavy-handed COVID mandates," DeSantis, a Republican, said in a statement.