US needs to hold on for another 2 or 3 months without easing up on Covid-19 measures, expert says. Here's what's at stake

And for several weeks, Covid-19 cases and hospitalizations were trending downward, with several local and state leaders reporting some of the lowest numbers they've seen in months.

"With these new statistics I am really worried about reports that more states are rolling back the exact public health measures we have recommended to protect people from Covid-19," Walensky said.

"That just doesn't seem like a very big burden to save other people's lives and maybe even your own life."

You asked, we answered: Your top Covid-19 and vaccine questions

Some leaders expecting first J&J doses as early as Tuesday

As the country works to vaccinate as many people as possible, local and state leaders are expecting their first doses of the Johnson & Johnson vaccine this week.

Three Federal Emergency Management Agency vaccination sites in Texas are expected to receive about 24,000 doses of the Johnson & Johnson vaccine Tuesday, according to Lara Anton, press officer for the Texas Department of State Health Services.

More than 200,000 Johnson & Johnson doses are expected to be available to the state for next week's allocation, Anton said.

In Houston, Mayor Sylvester Turner said he expects the first delivery of the Johnson & Johnson vaccine Tuesday.

"It certainly will be the best option for our transient populations," he said of the one-dose vaccine.

"For example, our homeless population, which is very difficult to get back for their second shot."

Track US Covid-19 vaccinations here

In Colorado, health officials said they expect to receive more than 45,000 doses of the vaccine by Friday.

Mike DeWine announced the state will receive more than 96,000 doses of the vaccine this week, boosting the state's total number of doses expected this week to more than 448,000.

Because of the additional doses, DeWine said the state will be expanding its vaccine eligibility to Phase 1C on March 4: individuals who are living with Type 1 diabetes, are pregnant, are bone marrow transplant recipients or living with ALS, as well as people working in childcare services, funeral services and law enforcement and corrections officers.

The state will also start its Phase 2 on the same day, lowering age eligibility to people 60 or older.