One week after public schools opened for the new school year, New York City Mayor Bill de Blasio announced new changes to student testing.

Starting Sept. 27, students in all grade levels will be tested weekly instead of bi-weekly. In addition, any student who is in a classroom with a positive case won't have to quarantine if they were masked and three feet distant, according to the mayor.

"We've been looking at these two issues over the last few weeks. We looked at it in light of the data from the first week of school, we decided to make both of these changes simultaneously, and they do complement each other," de Blasio said during his daily news conference.

The United Federation of Teachers had pushed the mayor to switch to weekly testing. All teachers must have at least one dose of the COVID-19 vaccine by Sept. 27, as part of the city's mandate for education employees.

CVS Health is launching a major hiring spree to fill 25,000 clinical and retail jobs in preparation for an expected increase in vaccine and testing demand in the months ahead.

The move is in anticipation of the need for COVID-19 booster shots and flu vaccines.

The positions will largely be for pharmacists, pharmacy technicians and nurses at their retail locations to be filled “as soon as possible,” the company announced Monday.

Pharmacy executives predict a far greater staffing need than usual this year, especially should flu season get severe and if COVID-19 boosters become authorized for more expanded groups. Pharmacies are also hoping to avoid a repeat of last year’s scenes of slammed testing sites and the chaotic start to the vaccine rollout.

“Every flu season we need additional team members,” said Neela Montgomery, the executive vice president of CVS health and the president of CVS Pharmacy. “But this year we’re looking for even more. With the continued presence of COVID-19 in our communities, we’re estimating a much greater need for pharmacists, trained pharmacy technicians, nurses, and retail store associates. These jobs offer a rewarding opportunity to really make an impact on public health in our country.”

A virtual hiring event Friday will spearhead the recruiting push.

-ABC News’ Sasha Pezenik

There is still uncertainty and questions to be answered regarding whether all Americans will be recommended to receive booster shots of the COVID-19 vaccine, said acting U.S. Food and Drug Administration Commissioner Dr. Janet Woodcock.

Woodcock spoke with former senior White House COVID-19 response adviser Andy Slavitt on his podcast program “The Bubble” on Monday, raising questions on what the booster shots may or may not do and discussing any uncertainties that could have factored into the FDA’s decision to recommend boosters only for high-risk Americans and those over the age of 65.

Right now, the FDA does not know enough about how an additional shot will impact transmissibility or about cellular immunity and whether T-cells are protected, among other factors, Woodcock said.

“Basically the FDA decision is, do the overall benefits outweigh the potential harms for any given vaccination and that’s how to proceed,” Woodcock said. “But obviously individuals benefit from not having a transmissible virus circulating around."

-ABC News’ Matthew Vann

In the wake of weeks of increasing COVID-19 cases and hospitalizations, the U.S. is once again experiencing a surge in virus-related deaths.

The average number of deaths in the U.S. has risen to more than 1,500 per day, an increase of about 20% in the last week and nearly eight times the death average from two months ago, when the national average dropped to a near-low of 191 deaths reported each day, according to data from the CDC and the Department of Health & Human Services.

Twenty-two states and Washington, D.C. are seeing increasing case averages, while seven states are experiencing increasing hospital admissions, according to the HHS.

However, overall hospitalizations in the U.S. are down, with about 10,000 fewer patients currently hospitalized compared to three weeks ago.

About 93,000 Americans are currently hospitalized. In recent weeks, there had been more than 103,000 patients receiving care across the country.

The drop is largely attributed to plummeting figures in Florida, where there are nearly 10,000 fewer patients hospitalized now, compared to a month ago.

The presence of the virus is shifting away from states in the deep South such as Florida, Louisiana and Mississippi, and further into other regions of the country that were not as hard hit in the first delta surge.

Tennessee and West Virginia currently have the country's highest case rate, followed by Alaska, South Carolina, Wyoming, Montana and Kentucky, which all have case rates above 500 per 100,000 people.

-ABC News’ Arielle Mitropoulos

School districts without a universal masking policy in place at the start of the school year saw a significant increase in COVID-19 outbreaks, according to three new studies released by the Centers for Disease Control and Prevention.

Additionally, school districts in those counties saw more than double the number of pediatric COVID-19 cases during this same period, the studies, released Friday, also found.

The studies further emphasize that school mask requirements, along with other prevention strategies, are critical to reducing the spread of COVID-19 in schools.

Other key findings from the studies include:

- Schools in Arizona that opened without a school mask requirement had a 3.5 higher likelihood of having a COVID-19 outbreak than schools that opened with a school mask requirement.

-During the early part of the 2021-2022 academic school year, almost 2,000 schools have been closed and more than 900,000 students in more than 40 states have been impacted.

- Pediatric cases during the start of the 2021-2022 school year were about half in U.S. counties with school mask requirements than in counties without school mask requirements.

To prevent COVID-19 outbreaks in schools, the CDC recommends a multi-layered strategy including vaccination, universal indoor masking, testing and physical distancing.

-ABC News' Eric Strauss