Dr. Francis Collins, director of the National Institutes of Health, said he expects children ages 5 to 11 in the United States to become eligible for COVID-19 vaccination toward the end of the year.

"Keep in mind, kids are not just scaled down adults -- they have different immune systems and metabolisms. You really have to do the careful trials to make sure you got the dose right and there aren't any surprises," Collins told ABC News' George Stephanopoulos in an interview Tuesday on "Good Morning America."

"Realistically," he added, "I don't think we're going to see approval for kids under 12 until late in 2021."

Collins also said there is “no reason to be too confident” that the country has hit its peak and that case numbers will start to come down.

"When I look at the data, it's still going up awfully steeply. More than 150,000 cases a day and that number keeps growing; hospitalizations [at] 95,000; deaths now averaging a 1,000 a day," he noted. "Florida, Louisiana, Mississippi, Alabama -- there's just a world of hurt going on there with so many unvaccinated people and hospitals really struggling to try to manage all the really sick people who are coming to their emergency rooms."

The delayed 2020 Summer Paralympics kicked off in Tokyo on Tuesday as Japan grapples with a growing COVID-19 crisis that has showed no signs of slowing down.

Protesters calling for the Games to be canceled gathered outside the Olympic Stadium in Japan's capital ahead of Tuesday's opening ceremony. Like the 2020 Olympics, which ended on Aug. 8, this year's Paralympics is taking place amid a state of emergency. More than a dozen Japanese prefectures, including Tokyo, are currently under emergency measures related to COVID-19. The Tokyo Olympics and Paralympics were both postponed a year due to the pandemic.

Japan's daily number of newly confirmed COVID-19 cases has been breaking records in recent days and weeks, while the daily death toll has stayed below the record 216 fatalities reported on May 18. The Japanese government and the Tokyo metropolitan government issued a joint appeal on Monday to hospitals in the capital to admit more COVID-19 patients as cases rise.

"The delta variant's strong infectiousness just isn't comparable to previous ones," Japanese Health Minister Norihisa Tamura said as he stood alongside Tokyo Gov. Yuriko Koike. "We would like to have further support from the medical community to secure hospital beds for coronavirus patients."

Memorial Hermann, one of the largest not-for-profit health systems in southeast Texas, said Monday it was forced to close three of its 24-hour emergency rooms in the Houston area "due to the continued COVID-19 surge."

The emergency rooms inside Memorial Hermann's convenient care centers in the Kingwood, Spring and Sienna neighborhoods will remain closed "until further notice."

"Patients who are currently receiving care inside any of these Emergency Rooms will be safely discharged or transferred to another Memorial Hermann facility," the health system said in an announcement on its website. "Members of our community who require emergent care should proceed to another nearby Emergency Center for assistance."

Hawaii Gov. David Ige is urging tourists to stay away from the state, which saw a huge number of visitors over the summer, due to the increase in COVID-19 cases.

“It is not a good time to travel to the islands. I encourage everyone to restrict and curtail travel to Hawaii,” Ige said at a news conference Monday.

The islands are dealing with a big COVID surge due to the delta variant, but have a limited number of hospitals. The governor even suggested that another full lockdown is on the table.

"Is a lockdown on the table? Yes, it would be if the number of cases continues to grow exponentially as it has in the last 10 weeks ... then we will have to take action to limit and ensure that the hospitals aren’t overrun," Ige said Monday.

-ABC News' Gio Benitez

Japan has suspended the use of about 1.63 million doses of Moderna's COVID-19 vaccine due to reported contamination, as the country grapples with surging infections.

Japanese drugmaker Takeda Pharmaceutical Co., which is in charge of distributing the Moderna vaccine in Japan, said in a press release Thursday that it has received reports of foreign substances in some unused vials at multiple inoculation sites. Although some doses might have been administered, Takeda said there have been no reports of safety concerns tied to the affected vials so far.

After consulting with Japan's Ministry of Health, Labor and Wealth, Takeda said it decided as a safety precaution to stop using doses from three separate lots, manufactured in the same production line as the contaminated vials. The company said it has requested Moderna to conduct an emergency investigation into the issue.

For doses from non-suspended lots, Takeda urged people to check the vials for discolouration, foreign substances or other abnormalities before continuing to use. Meanwhile, the Japanese health ministry said it will work with Takeda to supply alternative doses in an effort to minimize the impact on the country's vaccination progress.

Moderna told ABC News that it has put the 1.63 million doses on hold in Japan after being notified that some of the vials may have been contaminated. One of the three lots received "several complaints of particulate matter" in its vials, the American drugmaker said, while the two other adjacent lots were put on hold out of "an abundance of caution" and for continued assurance of quality.

According to Moderna, the manufacturing issue may have come from one of the lines used at its contract manufacturing site in Spain. The Massachusetts-based company said it is looking into the contamination reports and "proactively communicating with Japan’s health authorities and its partners as the investigation proceeds." Moderna added that it remains "committed to working transparently and expeditiously" with its Japanese distribution partner and with regulators to address any potential concerns. No safety or efficacy concerns have been identified so far, the company said.

Moderna noted that the pause in Japan does not impact doses distributed in the United States, or put the American supply at risk in any way.