A pandemic of the novel coronavirus has now killed more than 894,000 people worldwide.
Over 27.4 million people across the globe have been diagnosed with COVID-19, the disease caused by the new respiratory virus, according to data compiled by the Center for Systems Science and Engineering at Johns Hopkins University. The criteria for diagnosis -- through clinical means or a lab test -- has varied from country-to-country. Still, the actual numbers are believed to be much higher due to testing shortages, many unreported cases and suspicions that some national governments are hiding or downplaying the scope of their outbreaks.
The United States is the worst-affected country, with more than 6.3 million diagnosed cases and at least 189,538 deaths.
California has the most cases of any U.S. state, with more than 742,000 people diagnosed, according to Johns Hopkins data. California is followed by Texas and Florida, with over 659,000 cases and over 650,000 cases respectively.
Nearly 170 vaccine candidates for COVID-19 are being tracked by the World Health Organization, six of which are in crucial phase three trials.
Oxford/AstraZeneca vaccine trial temporarily on hold
AstraZeneca has paused its COVID-19 vaccine study being conducted with the U.K.'s University of Oxford due to a "potentially unexplained illness" in one of its trials, the pharmaceutical company said Tuesday.
“As part of the ongoing randomized, controlled global trials of the Oxford coronavirus vaccine, our standard review process was triggered and we voluntarily paused vaccination to allow review of safety data by an independent committee," the company said in a statement.
The action is in response to a "potentially unexplained illness in one of the trials," it said. "In large trials illnesses will happen by chance but must be independently reviewed to check this carefully."
AstraZeneca is one of the front-runners in the race for a COVID-19 vaccine and has received funding through the federal government's Operation Warp Speed. The company said it is "working to expedite the review of the single event" to minimize any impact on its trial timeline.
AstraZeneca did not note where the illness occurred in its statement. At least one U.S. site has put the trial on hold, ABC News has learned.
"AstraZeneca is having a review and evaluation of the trial this week and thus we are pausing enrollment for this to occur, upon completion of the evaluation we will be able to reschedule patients," The Lundquist Institute at Harbor-UCLA Medical said in a statement. The institute had just announced its first injections on Friday.
More than 513,000 US children have been diagnosed with COVID-19
In the U.S., 70,630 children were diagnosed with COVID-19 between Aug. 20 and Sept. 3, bringing the total number of kids and teenagers with the coronavirus in the nation to 513,415, according to a report released Tuesday from the American Academy of Pediatrics (AAP).
This marked a 16% increase in over two weeks, the AAP said, based on data compiled by the AAP and the Children's Hospital Association.
Children made up 9.8% of all reported coronavirus cases as of Sept. 3, the AAP said.
"The data -- while limited because of its reliance on how each state reports its cases -- underscores the urgent need to control the virus in communities before schools and businesses can reopen safely," the AAP said in a Tuesday press release.
ABC News' Eric Strauss contributed to this report.
Fauci expects 'multiple vaccines in 2021'
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, says, "my hope, my expectation, is that we'll have not one but multiple vaccines in 2021."
"Unless you have a perfect vaccine, which very few are, you'll always have people who end up sick," Fauci told The New Yorker. "With or without a vaccine, we're going to need other treatments."
When it comes to Operation Warp Speed -- the White House's public-private partnership aiming to deliver 300 million doses of a safe vaccine -- Fauci said he "never liked the 'warp speed terminology.'"
"It suggests, incorrectly, that you're rushing things," he told The New Yorker. "Whenever people hear things are being rushed, they worry about safety."
Fauci said the "warp speed" part actually relates to the money the government put into vaccine production.
"If a vaccine doesn't work, you've lost a few hundred million dollars," Fauci said. "If it does work, if it's safe and effective, you've saved four, five, six months of waiting to get people the vaccine. That's huge."
4 more states added to New York, New Jersey, Connecticut quarantine list
Delaware, Maryland, Ohio and West Virginia were added on Tuesday to a quarantine list regulated by New York, New Jersey and Connecticut.
Thirty-five states and territories are currently on the travel advisory list, which applies to any area with a positive test rate higher than 10 per 100,000 residents or 10% or highest positivity rate over a one-week rolling average.
"It remains critically important for anyone arriving to New Jersey from these 35 states and territories to get tested for COVID-19 and self-quarantine for 14 days," New Jersey Gov. Phil Murphy said in a statement Tuesday.
States and territories that currently qualify for the list are: Alabama, Alaska, Arkansas, California, Delaware, Florida, Georgia, Guam, Hawaii, Iowa, Idaho, Indiana, Illinois, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Missouri, Mississippi, Montana, North Carolina, North Dakota, Nebraska, Nevada, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin and West Virginia.