Coronavirus updates: Los Angeles to prohibit gatherings, close playgrounds

The actual number of people infected with the novel coronavirus in the United States reached nearly 53 million at the end of September, according to a model developed by scientists at the Centers for Disease Control and Prevention.

The scientists estimated the cumulative incidence of COVID-19 in the U.S. population by taking the laboratory-confirmed case counts that were reported nationally and adjusting them for sources of under-detection based on testing practices in inpatient and outpatient settings. Preliminary estimates using the model found that 2.4 million hospitalizations, 44.8 million symptomatic illnesses and 52.9 million total infections may have occurred through Sept. 30.

"This indicates that approximately 84% of the U.S. population has not yet been infected and thus most of the country remains at risk, despite already high rates of hospitalization," the scientists wrote in a report published in the Nov. 25 issue of the journal Clinical Infectious Diseases.

There were 6.9 million laboratory-confirmed cases of of domestically-acquired infections that were detected and reported nationally through Sept. 30. Since then, the CDC's tally has increased to nearly 12.5 million. Based on the model's ratio, the true estimated total would now be more than 95 million.

U.K. Health Secretary Matt Hancock said Friday that he has formally asked the country's medicines regulator to assess whether a COVID-19 vaccine developed by AstraZeneca and the University of Oxford "meets rigorous safety standards."

The move comes amid questions about preliminary results from late-stage trials of the vaccine candidate, called AZD1222, after the England-based pharmaceutical giant and the university acknowledged that the most positive findings actually stemmed from a dosing error.

On Monday, researchers announced the interim analysis of Phase 3 trials in the United Kingdom and Brazil, which looked at two different dosing regimens. One regimen showed vaccine efficacy of 90% when AZD1222 was given as a half dose, followed by a full dose at least one month apart. A second regimen showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens showed an average efficacy of 70%.

Mene Pangalos, AstraZeneca's executive vice president of biopharmaceuticals research and development, later revealed during an interview with Reuters that the half-dose regimen was "serendipity." A portion of the trial -- less than 3,000 volunteers -- had received a lower initial dose by accident, which was only discovered as the group experienced far milder side effects.

"So we went back and checked," Pangalos told Reuters, "and we found out that they had under-predicted the dose of the vaccine by half."

The COVID-19 vaccine candidate is the second to reach the formal assessment stage in the United Kingdom, following one developed by New York City-based pharmaceutical company Pfizer and its German partner BioNTech.

Moscow saw a 311% month-to-month increase in COVID-19 deaths for October, health authorities said.

According to the Moscow Healthcare Department, the Russian capital reported 543 COVID-19 deaths in September followed by 2,235 deaths in October -- an increase of more than 311% -- as a second wave of the coronavirus pandemic swept the country.

Meanwhile, Russia reported a sharp increase in COVID-19 infections on Friday, with the country's coronavirus response headquarters confirming a record 27,543 new cases in the last 24 hours. An additional 496 new deaths from the disease were also registered nationwide in the past day. The country's cumulative total now stands at 2,215,533 confirmed cases, including 38,558 deaths.

Moscow continues to be the epicenter of Russia's COVID-19 outbreak and recent surge. The city accounted for nearly 29% of the newly reported cases and more than 15% of the newly registered deaths, according to the country's coronavirus response headquarters.

The Eastern European nation of 145 million people has the fifth-highest tally of COVID-19 cases in the world, behind only the United States, India, Brazil and France, according to a real-time count kept by Johns Hopkins University.

ABC News' Alina Lobzina contributed to this report.

There were 110,611 new cases of COVID-19 confirmed in the United States on Thursday, the day of Thanksgiving, according to a real-time count kept by Johns Hopkins University.

It's the 24th straight day that the country has reported over 100,000 newly diagnosed infections. Thursday's count is down from a peak of 196,004 new cases on Nov. 20.

An additional 1,232 fatalities from COVID-19 were also registered nationwide on Thursday, less than the all-time high of 2,609 new deaths on April 15.

COVID-19 data may be skewed this week and next due to possible lags in reporting over Thanksgiving followed by a potentially very large backlog from the holiday.

A total of 12,885,299 people in the United States have been diagnosed with COVID-19 since the pandemic began, and at least 263,462 of them have died, according to Johns Hopkins. The cases include people from all 50 U.S. states, Washington, D.C. and other U.S. territories as well as repatriated citizens.

Much of the country was under lockdown by the end of March as the first wave of pandemic hit. By May 20, all U.S. states had begun lifting stay-at-home orders and other restrictions put in place to curb the spread of the novel coronavirus. The day-to-day increase in the country's cases then hovered around 20,000 for a couple of weeks before shooting back up and crossing 100,000 for the first time on Nov. 4.