(CNN)Though many Americans are eager to return to normal after a year of living through the Covid-19 pandemic, the head of the Centers for Disease Control and Prevention (CDC) on Wednesday reminded Americans that "we're not quite there yet."
"We are so close -- so very close to getting back to the everyday activities we all miss so much, but we're not quite there yet," CDC Director Dr. Rochelle Walensky said at a White House Covid-19 Response Team news conference.
"This is a critical moment in our fight against the pandemic," she said, noting that Americans still need to follow public heath guidelines for social distancing, mask use and hand washing.
"I know this is not easy and so many of us are frustrated with the disruption this pandemic has had on our everyday lives, but we can do this as a nation working together," she said. "There is reason to be hopeful because we now know so much more about this virus."
More than 30 million coronavirus infections have been reported in the country, according to Johns Hopkins University(JHU), and almost 552,000 people have died from Covid-19.
After a decline in cases nationwide in recent weeks, the US just saw a jump. More than 66,870 new Covid-19 cases a day on average were reported over the past week, as of Monday. That is a 24.6% increase over the week prior, when the average had fallen to its lowest point of 2021, according to JHU data.
Virus variant might be dominant already, expert says
The more contagious B.1.1.7 variant, first identified in the UK, which heath experts think is partly driving an uptick of cases in some states, may already be dominant across the country.
"I think we are there," said William Lee, vice president of science at Helix, a company whose tests have identified a large share of variant cases across the country. "But at the end of the day, it's hard to say for sure," given gaps and delays in the data.
Lee co-authored a study published Tuesday in the journal Cell that estimates the variant would cause the majority of Covid-19 cases in the US by March 19.
According to that study, B.1.1.7 cases are expected to double every week and a half as a percentage of the country's total coronavirus cases. The study's conclusions were based on testing data through February.
Lee said that there is strong evidence the variant is already responsible for a majority of cases in states like Georgia, Florida and Michigan. Helix's data does not include robust samples from a number of other states, particularly in the Northeast and Midwest regions.
Walensky, however, told reporters Wednesday the variant is "about 26% of circulating virus right now," according to the latest data the CDC has. Her comment appears to be based on preliminary data of samples collected in the two weeks leading up to March 13, according to the agency's website.
"It is starting to become the predominant variant in many US regions," she added.
Preliminary data suggests that the three vaccines that have so far won emergency use authorization from the US Food and Drug Administration "may provide some protection against a variety of strains, including B.1.1.7 (originally identified in the United Kingdom)," the CDC says in its guidance for fully vaccinated people.
Dr. Ashish Jha told CNN on Wednesday that while the pace of people getting shots has increased, the number of new cases each week likely will still increase.
"Our vaccinations are going great, but not enough to keep up with the B.1.1.7 variant," he said.
Only about 16.4% of the US population has been fully vaccinated, according to the CDC.
In February, Pfizer and Moderna said they were testing vaccine strategies against variants like the B.1.1.7 lineage.
The National Institutes of Health said Wednesday it has started a clinical trial of Moderna's vaccine designed to protect against another concerning variant, the B.1.351 lineage, first identified in South Africa.
Michigan governor thinks B.1.1.7 is driving surge there
Michigan has seen one of the highest Covid-19 case increases over the last week by percentage -- 52%, according to Johns Hopkins -- and its governor said Wednesday she believes B.1.1.7 is one of the reasons.
Its current seven-day average, 5,409 cases a day, is Michigan's highest since mid-December.
"We haven't abandoned our protocols; it's just that we've got a higher proportion of variants," Gov. Gretchen Whitmer told CNN's "New Day." "And part of that is people getting tired, there's fatigue, and there's variants and there's more travel."
Michigan has the country's second-highest total of reported B.1.1.7 cases in the country, according to the CDC. The count represents only B.1.1.7 cases caught in surveillance analysis of positive samples, and so the variant's actual presence is likely higher than reported.
The state has a mask mandate and restrictions on restaurant and gym capacity, though capacity restrictions were recently eased. She said there are always robust discussions about whether to tighten restrictions, but "what we need to do is double down on our masking and get more people vaccinated."
Vaccine expert thinks adolescents could start inoculations in summer
More than 97 million people have received at least one dose of a vaccine -- roughly about 29% of the US population -- and nearly 55 million people are fully vaccinated, CDC data shows.
More than half of the country's 65 and older population -- 50.8% -- are fully vaccinated and more than seven out of 10 seniors in the US have received at least one dose, the data shows.
No vaccine has been authorized in the United States for children 15 and younger. But Pfizer and BioNTech on Wednesday released news that could impact inoculations later this year: Their Covid-19 vaccine was 100% effective and well tolerated in youths ages 12-15 in a clinical trial, the companies said.
Pfizer/BioNTech said they intend to submit the data as soon as possible for expanded emergency use authorization of their two-dose vaccine for those ages to the US Food and Drug Administration.
Pfizer also is conducting a Phase 1/2/3 study of its vaccine in children ages 6 months to 11 years, and results are expected by the end of the year.
One vaccine expert said that assuming the FDA authorizes expanded use, he could see that age range begin to get vaccinated this year.
"I think there is some urgency to try to do this by the fall (for school reopenings), and so I think over the summer, I wouldn't be surprised if we started seeing adolescents get vaccinated," Dr. Peter Hotez, co-director of the Center for Vaccine Development at Texas Children's Hospital, told CNN on Wednesday.
More than a dozen states have opened vaccine eligibility to everyone 16 and older, and every other state has announced plans to do so by at least May 1.
Pfizer's vaccine is the only one available for people 16 and older.
Moderna also is testing its Covid-19 vaccine in adolescents and children: One trial in children ages 12-17, and another for 6 months to 11 years.
Covid-19 was third leading cause of death last year, CDC confirms in early data
Covid-19 was the third leading cause of death in the United States last year, after heart disease and cancer, according to provisional data released Wednesday by the CDC.
Unintentional injury and stroke were fourth and fifth, respectively.
Overall, the US death rate increased by 15.9% between 2019 and 2020 -- from 715.2 to 828.7 deaths per 100,000 people, according to the report.
The data is provisional; the numbers and death rates might change as additional information is received. Since investigating causes of death takes time, final data for a given year is typically published about 11 months after the end of the calendar year.
Life expectancy in the United States also dropped a full year in the first half of 2020, according to a provisional report published by the CDC's National Center for Health Statistics in February. The report shows that US life expectancy fell to 77.8 years, back to what it was in 2006.
Wisconsin's Supreme Court strikes down mask mandate
While some governors recently lifted mask mandates, Wisconsin's governor is unwillingly watching his vanish.
The Wisconsin Supreme Court on Wednesday effectively struck down that state's mask mandate, by ruling Gov. Tony Evers did not have authority to issue successive health emergency declarations.
Evers, facing opposition from the Legislature, used emergency declarations to institute statewide mask mandates. The court noted that it wasn't ruling on whether the mask mandate was wise, but only that Evers' successive declarations bypassing the Legislature weren't legal.
Evers responded to Wednesday's ruling by asking residents to keep wearing masks, even without a mandate. "We still need Wisconsinites to mask up so we can beat this virus," he said.
Earlier this week, President Joe Biden made a plea to the nation's leaders to reinstate mask mandates, adding, "this is not politics."
Mississippi Gov. Tate Reeves, who lifted all county mask mandates earlier this month, responded through Twitter.
"Let me get this straight -- POTUS Biden wants Mississippi to reverse course and reinstate a mask mandate because cases are going up in New York and New Jersey," Reeves wrote.
"No thank you, Mr. President," he added.
Arkansas Gov. Asa Hutchinson announced Tuesday he was lifting a statewide mask mandate, adding that businesses were free to require customers to wear masks.
And Alabama Gov. Kay Ivey will move ahead with her plan to end the state's mask mandate next week, a spokesperson for the governor told CNN this week.
