Just 20% of people in low and lower-middle-income countries have received their first vaccine dose, compared to 80% of people in high and upper-middle income countries, according to the World Health Organization and COVAX, the initiative aiming to provide equitable vaccine access across the world.

"The global picture of access to COVID-19 vaccines is unacceptable," COVAX said, adding that its ability to reach lower income countries is "hampered by export bans, the prioritisation of bilateral deals by manufacturers and countries, ongoing challenges in scaling up production by some key producers, and delays in filing for regulatory approval."

COVAX said it expects to have access to 1.425 billion doses of vaccine this year, with about 1.2 billion available for lower income economies participating in COVAX's Advance Market Commitment.

"This is enough to protect 20% of the population, or 40% of all adults, in all 92 AMC economies with the exception of India. Over 200 million doses will be allocated to self-financing participants," COVAX said. "The key COVAX milestone of two billion doses released for delivery is now expected to be reached in the first quarter of 2022."

-ABC News' Kirit Radia

The United States has recorded more than 40 million confirmed cases of COVID-19, including over 650,000 deaths, since the start of the pandemic, according to real-time data compiled by the Center for Systems Science and Engineering at Johns Hopkins University.

The U.S. surpassed the grim milestone on Tuesday, as the highly contagious delta variant continued to spread across the nation. The U.S. has reported more COVID-19 cases and deaths than any other country in the world.

The U.S. reported 251,781 COVID-19 cases among kids during the week ending Sept. 2 -- the highest week of pediatric cases since the pandemic began, according to the weekly report from the American Academy of Pediatrics and the Children’s Hospital Association.

After declining in the early summer, new cases among kids are rising "exponentially," the organizations wrote, with the weekly figure now standing nearly 300 times higher than it was in June, when just 8,400 pediatric cases were reported over the span of one week.

Last week children represented 26.8% of all reported COVID-19 cases. Regionally, the South had the highest number pediatric cases, accounting for approximately 140,000 of last week's cases.

The rate of pediatric hospital admissions per 100,000 people is also at one of its highest points of the pandemic, up by 600% since the 4th of July, according to federal data.

Severe illness due to COVID-19 remains "uncommon" among children, the two organizations wrote in the report. According to the nearly two dozen states which reported pediatric hospitalizations, 0.1%-1.9% of all child COVID-19 cases resulted in hospitalization. ​Similarly, in states which reported virus-related deaths by age, 0.00%-0.03% of all child COVID-19 cases resulted in death.

However, the AAP and CHA warned that there is an urgent need to collect more data on the long-term consequences of the pandemic on children, "including ways the virus may harm the long-term physical health of infected children, as well as its emotional and mental health effects."

About 37.7% of children ages 12 to 15 and 46.4% of adolescents ages 16 to 17 have been fully vaccinated against COVID-19.

-ABC News' Arielle Mitropoulos

The country's daily death average continues to surge, now standing at more than 1,100 deaths reported a day. This marks the nation's highest average in nearly six months.

On Tuesday, the death toll crossed 650,000 Americans lost to the virus, according to data from Johns Hopkins University, meaning that 1 in every 504 Americans has died from the virus.

The U.S. COVID death toll is now more than 218 times higher than the number of lives lost during the U.S. attacks on Sept. 11. It is also rapidly approaching the total number of American deaths that were recorded during the 1918 influenza pandemic.

Prior to the Labor Day holiday, the U.S. daily case average stood around 150,000 cases a day. About a year ago, around Labor Day, the country was averaging about 38,000 new cases a day.

-ABC News' Arielle Mitropoulos