Nearly 21 percent of high school seniors say they vaped within the past 30 days, up from 11 percent one year ago, a new survey out Monday says.

The Monitoring the Future survey has been in existence for 44 years, asking teenagers whether they use drugs, drink alcohol, or smoke, and this was the most dramatic spike in its history. The survey is funded by the National Institute on Drug Abuse, and its director, Nora Volkow, said the report is "very worrisome. We are very concerned about the increase in vaping."

Vapors from e-cigarettes contain high levels of nicotine, and doctors fret about how this affects brains that are still developing. The survey also found that more teens now believe that they are simply breathing in flavors when they vape, not understanding that they are indeed inhaling nicotine. Catherine Garcia

The World Health Organization is temporarily halting a study on hydroxychloroquine and chloroquine as potential COVID-19 treatments due to safety concerns.

WHO Director-General Tedros Adhanom Ghebreyesus announced the decision on Monday, after a study published in The Lancet medical journal suggested COVID-19 patients treated with hydroxychloroquine and chloroquine were more likely to die, CNN reports. The drugs were being reviewed as part of the WHO's Solidarity Trial — a coronavirus research effort involving more than 400 hospitals in 35 countries.

President Donald Trump last week revealed he takes hydroxychloroquine as a preventative measure against COVID-19, despite there being no evidence of its effectiveness and the FDA cautioning against the drug due to serious side effects including abnormal heart rhythms. Meanwhile Brazilian President Jair Bolsonaro is touting the other drug halted in the study, chloroquine.

The Data Safety Monitoring Board will review data about the drugs to assess whether they should continue to be used in the trial, though other arms of the trial will carry on, per CNN.

Tedros noted the halt concerns hydroxychloroquine and chloroquine as they pertain to COVID-19. "I wish to reiterate that these drugs are accepted as generally safe for use in patients with autoimmune diseases or malaria," he said. Taylor Watson

Biden is back.

Former Vice President Joe Biden on Monday made his first public appearance since mid-March as he visited a veterans memorial in Delaware, notably clad in a mask. The presumptive Democratic presidential nominee laid a wreath in honor of Memorial Day, alongside his wife, Jill Biden, who also wore a mask.

Biden's choice to follow the Centers for Disease Control and Prevention recommendation to wear a mask during the coronavirus pandemic is in stark contrast to President Donald Trump, who often refuses to wear masks in public, fearful that he'd look ridiculous.

Biden's first outing in two months may serve as a trial run for public events, reports The Associated Press, suggesting he won't spend the remaining five months until the election campaigning from home. While advisers hope to resume campaign activities eventually, they intend to do so "when safety allows, and we will not do that a day sooner," said Biden campaign manager Jen O'Malley Dillon, per AP. Taylor Watson

The Trump administration sent Congress a national coronavirus testing strategy in time to meet a Sunday deadline, The Washington Post reported, citing a copy of the 80-page "Covid-19 Strategic Testing Plan" it obtained.

The report promises that the federal government will buy 100 million swabs by the end of 2020, and distribute them to states to help them expand testing. The document did not outline federal testing goals for each state, rather it listed testing targets states reported to federal officials for May. Public health officials say broader testing to determine who has been infected with the novel coronavirus and who might have immunity are key curbing the spread of the outbreak and allowing the economy to fully reopen.

The administration plan calls for every state to try to test at least 2 percent of its population in May and June. Read more at The Washington Post. Harold Maass

A federal judge has ruled that a Florida law requiring felons to pay all court fines and fees before they can register to vote was unconstitutional.

Judge Robert Hinkle of the United States District Court in Tallahassee wrote that the restrictions amounted to a poll tax that would prevent voting by people who can't afford to pay, The Washington Post reports. "The Twenty-Fourth Amendment precludes Florida from conditioning voting in federal elections on payment of these fees and costs," Judge Hinkle wrote, calling the state law a "pay-to-vote system."

Per Hinkle's order, the state must tell felons what they owe and whether they are eligible to vote — if felons don't receive this information within 21 days, they are allowed to register, the Post reports.

Republican lawmakers and Gov. Ron DeSantis (R) pushed through the law after voters overwhelmingly approved a 2018 constitutional amendment restoring voting rights for felons who have completed their sentences, including probation and parole. A DeSantis spokesperson said Sunday the governor's office is examining the ruling. Harold Maass

President Trump in series of tweets Monday morning threatened to pull the 2020 Republican National Convention out of North Carolina.

Trump tweeted that North Carolina Gov. Roy Cooper (D) is "still in shutdown mood" and said he would be forced to move the convention if not "immediately" given an answer as to whether coronavirus restrictions will be lifted, allowing "full attendance" in the Spectrum Center arena in Charlotte. Trump's tweets "blindsided" those involved in planning the convention, set to be held in late August, CNN reports. The Spectrum Center arena has a capacity of more than 17,500 people.

Vice President Mike Pence reiterated the Trump's comments, telling Fox News he looks forward to a swift response from Cooper, and "if need be, moving the national convention to a state that is farther along on reopening and can say with confidence that we can gather there."

Cooper told CNN his decision will not be political or emotional. "This is based on health experts, data and science and that's it for everybody to see." Taylor Watson

The U.S. is likely to impose sanctions against China if it enacts a new national security law that would erode Hong Kong's autonomy, White House National Security Advisor Robert O'Brien said Sunday.

The legislation, announced last week during China's National People's Congress, will allow Beijing to take over in Hong Kong, O'Brien said. That would make it unlikely that Secretary of State Mike Pompeo could certify that the city, a former British colony, had a "high degree" of autonomy, which would result in sanctions against China under the Hong Kong Human Rights and Democracy Act of 2019, O'Brien said.

The comments came as thousands of people gathered in Hong Kong streets to protest the proposed security law, and Hong Kong police fired tear gas to disperse the crowds. Read more at CNBC. Harold Maass