US data shows a big decline in new Covid-19 cases. Here's why it could be deceptive

(CNN)The United States is seeing a large decline in new Covid-19 cases -- but there's a major caveat.

According to a CNN analysis of data from Johns Hopkins University, the US is seeing a 29% decline in new Covid-19 cases compared to this time last week, the steepest one-week decline the country has seen during the pandemic.

Improvements have been made; in a White House briefing Friday, US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said the US continues to see a five-week decline, with the seven-day average of cases declining 69% since peaking on January 11.

But it's unclear exactly how much of the decline can be attributed to the winter weather that's gripped much of the country, forcing officials to close testing sites, which affects the collection of crucial data.

Several states impacted by winter storms are seeing large declines in new cases this week, per Johns Hopkins data, including Texas, where cases are down 56% compared to last week.

The COVID Tracking Project said Thursday it had been unable to update the daily number of tests performed in Texas for four days because of the winter weather. Overall, the US has seen nearly a 13.5% decrease in testing compared to this time last week.

Again, that's not to say the United States hasn't made progress in driving down case numbers. Early this week, Dr. Ashish Jha, dean of the Brown University School of Public Health, and Dr. Jonathan Reiner, professor of medicine and surgery at George Washington University, both pointed to increased mask-wearing as one reason for declining numbers.

Whatever progress has been made, however, is also threatened by the rise of Covid-19 variants, some of which appear to be more transmissible. And while they could spell trouble, pharmaceutical companies and scientists are confident vaccines will evolve with them, according to senior White House adviser Andy Slavitt.

'Racing ahead of the variant'

"I spoke to all the pharmaceutical companies and scientists, and they all say the same thing: Even if these vaccines diminish a little bit, they will be able to continually update them," Slavitt, who is responsible for the Covid-19 response, told CNN's Chris Cuomo Thursday.

With more than 1,500 cases of variants reported in the US, officials have been racing to administer vaccines quickly to get ahead of further mutations, with about 59.5 million doses administered so far across the country, according to the CDC.

"Even though the numbers look promising in terms of new cases going down, that's misleading," said Dr. Peter Hotez, dean of tropical medicine at Baylor College in Houston, pointing to the UK Covid-19 variant. "I think we're about to get hit very hard, so we have to race ahead of the variant."

New research out of Israel and Canada has found that only a single dose of the Pfizer/BioNTech's vaccine offers significant protection against the virus, but Slavitt stressed that does not mean people should skip the second dose.

"We don't know how long or how durable that benefit is without the booster," he said. "We don't know how effective it is against variants."

Dr. Anthony Fauci echoed that in Friday's White House briefing, saying he had not changed his mind after reading the Israeli report. He said the US would "stick with the scientifically documented efficacy and optimal response" of two doses.

He added he worried that if a large number of people received just one dose and had less optimal immune response, they could be exposed to the virus and start incubating viral mutations.

"You might theoretically be inducing new variants," he said.

Fauci says we need a universal vaccine

Because coronaviruses like Covid-19 have pandemic potential, the world needs a universal coronavirus vaccine, Fauci said Friday in an interview hosted by Georgetown University.

"I believe that we have the capability scientifically to develop what we call the universal coronavirus vaccine," he said. "In other words, one that really covers at least all of the SARS-CoV-2 mutations, but also the entire spectrum of the family of coronaviruses."

Also on Friday, the CEO of Pfizer said the company is adding a facility in Kansas to its Covid-19 fill-finish vaccine production process and expanding Covid-19 vaccine production capabilities at locations in Michigan and Connecticut.

CEO Albert Bourla said production improvements have allowed the company to reduce their timelines "from approximately 110 days from start to vial ready" and are now closer to "an average of 60 days, which is an almost 50% improvement."

The press conference was held jointly with President Joe Biden after he had toured the Pfizer production site in Kalamazoo, Michigan.

US will have to work 'double time' after winter weather

More than 41 million people have received at least one dose of the vaccine, and more than 17 million have received two doses, CDC data shows. But that means just 4.9% of the US population has been fully vaccinated.

A number of states have reported delays in vaccine deliveries, forcing providers to cancel or reschedule appointments for vaccinations.

But Slavitt said Friday night that states will receive more doses of Covid-19 vaccines than they "have ever received before" in the coming days.

"Starting tomorrow, Saturday, we're going to be shipping more doses than states have ever received before," Slavitt told CNN's Wolf Blitzer. "Because we're going to be shipping this week's doses and next week's doses."

Slavitt said it means that "for all the governors and all the states that have said we want more vaccines, they're going to have to be ready, they're going to have to make more appointments, they're going to have to extend their hours."

UPS and FedEx will make deliveries of vaccines on Saturday, and employees at the Moderna vaccine packaging plant will be working through the weekend to package backlogged orders to make them available for delivery early next week, Slavitt said. The government is also asking vaccine sites to extend their hours and schedule additional appointments to make up for lost progress, on top of rescheduling the canceled appointments.

Black and Hispanic people are getting fewer vaccinations

Kaiser Family Foundation (KFF) researchers analyzed state-level data for the 34 states that collect demographic information on Covid-19 vaccinations as of February 16.

In most of those states, Black and Hispanic people have received a smaller share of vaccinations compared to their share of cases, deaths and percentage of the population, the researchers noted. The opposite is true for White people in most states.

In Texas, for example, Hispanic people account for 42% of coronavirus cases, 47% of Covid-19 deaths and 40% of the state's population -- but they have gotten just 20% of vaccinations.

Among 27 states that report ethnicity data for those who have received at least one dose of the vaccine, White people have been vaccinated at a rate three times higher than Hispanic people and twice as high as Black people.

The KFF team noted that some states don't record the race or ethnicity of those vaccinated.

Vaccine studies continue for more groups

Fauci said Friday the US should have vaccine safety data for high school-age youths by the beginning of the fall, though data for younger children will probably not be available until next year.

In the White House briefing, Fauci pointed to Pfizer, which he said was set to study their vaccine for 12-year-olds down to 5- or 6-year-olds beginning in April. But information from those studies will likely not be available until the first quarter of 2022.

"However, we anticipate data on high school age individuals, namely individuals 12 years old to 17 years old, by the beginning of the fall," Fauci said. "Maybe not exactly coinciding with the first day of school, but sometime in the fall we will have that."

A Pfizer/BioNTech vaccine trial for pregnant women gave their first participants doses on Thursday. The doses were administered to US participants, though the trial will be conducted in nine countries: the United States, Canada, Argentina, Brazil, Chile, Mozambique, South Africa, the United Kingdom and Spain.

The company said the trial is designed to evaluate the vaccine in pregnant women, but also their infants, who will be monitored for safety and for the transfer of potentially protective antibodies until they're about 6 months old.

Pfizer/BioNTech also expects to expand trials to children ages 5 to 11 in the next couple of months, according to a company news release.