New York City Health Commissioner Dave Chokshi said he's issuing an advisory allowing all adults to receive a booster, as long as it's been six months since their last Moderna or Pfizer dose or two months since the Johnson & Johnson shot.

Chokshi asked New York City health care providers to "proactively reach out to their eligible patients -- particularly those 65 and older, those with medical conditions, and those who have received a Johnson & Johnson dose."

New York City is seeing an uptick in cases in recent days, Chokshi tweeted, adding that "booster doses can provide one more layer of reassurance, allowing us to breathe a bit easier, either for ourselves or our loved ones, particularly as we gather and travel around the holidays."

Young children can now get vaccinated against COVID-19 in Austria's capital as part of a new pilot project.

Starting Monday, about 200 children ages 5 to 11 can receive the low-dose Pfizer-BioNTech vaccine per day in Vienna. Registration for the pilot project, which is limited to the capital, opened over the weekend and more than 9,000 appointments have since been booked, according to Austrian newspaper Kurier.

The Pfizer-BioNTech vaccine can only be used "off-label" in this instance, because the European Medicines Agency has not yet authorized the shot for use in this younger age group.

Meanwhile, a nationwide lockdown for all unvaccinated individuals over the age of 12 began Monday at midnight. Residents who are not inoculated against COVID-19 are barred from leaving their homes except for basic activities such as work, grocery shopping, going for a walk or getting vaccinated.

Israel's Ministry of Health announced Sunday that children ages 5 to 11 would be eligible for vaccination against COVID-19.

The decision follows an advisory panel's approval last week of the low-dose Pfizer-BioNTech vaccine for 5- to 11-year-olds.

"The majority of experts on the committee were of the opinion that the benefit of vaccinating this age group outweighed any risk," the health ministry said in a statement Sunday.

A starting date for the inoculation campaign will be announced soon, the health ministry said. COVID-19 vaccination for this age group will not be made mandatory and parents will be given the choice to decide.

More than 62% of Israel's 9.2 million people have already received two doses of a COVID-19 vaccine, while nearly 44% have also gotten a booster shot, according to data from the health ministry.

-ABC News' Bruno Nota

For the second week in a row, the U.S. experienced an increase in its weekly number of pediatric COVID-19 cases.

Over the last week, more than 122,000 child cases were reported — an increase of about 22% from two weeks ago, according to a new report from the American Academy of Pediatrics (AAP) and the Children’s Hospital Association (CHA).

This marks the 14th consecutive week that child COVID-19 cases are above 100,000.

Prior to the recent increases, infections among children had been steadily dropping since the pandemic peak of 252,000 child cases, recorded over the span of a week in early September.

But now, COVID-19 cases among children remain "extremely high," the organizations wrote, and since the first week of September, there have been almost 1.6 million additional child cases.

Last week, children accounted for more than a quarter (27%) of reported weekly COVID-19 cases, though children under 18 make up just 22.2% of the U.S. population.

-ABC News’ Arielle Mitropoulos