We tried asking nicely. It's time to mandate COVID vaccines for some.

As a new wave of COVID-19 infections sweeps across the country driven by a highly contagious variant, an era of carrot incentives to increase the number of fully vaccinated Americans has played itself out.

Enticements ranging from hard scientific facts to Krispy Kreme doughnuts and million dollar lotteries are failing. Months after making free shots available, less than half the U.S. population is fully vaccinated. One hundred million eligible recipients simply say no.

Time has come to use the stick.

Highest rate of vaccine opposition

Requiring proof of vaccination – whether it's to board an airplane, attend a university or even to keep a job – certainly carries the risk of further inflaming a ridiculous cultural war (fueled by conspiracy theories and false information) over vaccinations. It's shameful that apart from Russia, the United States has the highest rate of vaccine opposition.

But the harsh reality is that infections have risen sevenfold in the past six weeks, and more than 97% of those being hospitalized are among the unvaccinated, with spikes in states where inoculation rates are lower than the national average – including Arkansas, Florida, Louisiana and Missouri.

That infections are nearly twice as common in counties that voted for Donald Trump compared with those that voted for Joe Biden bears witness to the politicization of a health crisis.

400 kids have died in USA

Hospitals are again overflowing, deaths are on the rise and those who cannot take the shot, including children under 12 and people with underlying health issues, are at growing risk of falling ill. More than 400 children in America have died in the pandemic.

COVID-19 constraints that people were thrilled to see go away have once more become guidance. The economic recovery is again at risk.

And even worse, every unvaccinated person sickened by COVID-19 offers the virus a host where mutations can render something even more horrible – a new variant that might conceivably defeat current vaccines.

This latest outbreak did not have to happen. So what to do about that?

A federal mandate broadly requiring vaccinations for all may be legally impossible and almost certainly unenforceable. (Though individual states may have more power in this regard.) But there are other steps Biden and private businesses can and must take immediately:

►The president reportedly plans to announce Thursday that all federal employees and contractors, upwards of 6 million people, either be vaccinated or submit to regular testing. (The Department of Veterans Affairs already announced this move for its health workers.) That's an excellent start, particularly after Biden made plain when he was president-elect his opposition to vaccine mandates. New York and California are taking similar steps with their public workers.

Biden should require the same of more than 2 million U.S. troops, only 51% of whom are even partially vaccinated. Service members already must receive more than a dozen other vaccines.

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►Biden should order that airlines require passengers to show proof of vaccination to fly, citing his authority over Federal Aviation Administration and interstate commerce. And he should order similar restrictions on interstate bus and rail service. Airlines alone process nearly 2 million passengers a day.

►The president must act to increase the number of young adults who are vaccinated, only about 30% of whom have received their shots. Hundreds of colleges are requiring in-person attendees be vaccinated, and Biden could boost this by conditioning federal student loans on proof of vaccination.

►Private companies must make jobs dependent on vaccination. Businesses as varied as United Airlines, Wall Street brokerages, The Washington Post and the Broadway production of "Hamilton" are already doing this. The Equal Opportunity Employment Commission says federal law allows such restrictions. Many more businesses must follow suit.

Critics will say COVID-19 vaccines still lack final approval by the Food and Drug Administration, which has granted only emergency authorization. But that's a distinction without a practical difference. More than 340 million dosages have been administered, with results scrutinized for efficacy and safety. It may be a few months before the FDA concludes its largely bureaucratic review, and the virus has its own expedited timetable as tens of thousands are hospitalized.

Vaccine mandates will certainly unleash angry reactions from those on the right arguing infringement on the freedom of personal choice. But a famous remark often attributed to the jurist Oliver Wendell Holmes is that "the right to swing my fist ends where the other man's nose begins."

A refusal to be vaccinated is like a wildly thrown fist. Noses are being figuratively bloodied across the country.

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This article originally appeared on USA TODAY: Biden, businesses must mandate the COVID vaccination shot for some