A drop in Covid-19 cases can be deceptive, official warns.

Here's how the US can stay ahead of a variant-driven surge

Although the rise of COVID-19 variants in the United States could spell trouble, pharmaceutical companies and scientists are confident vaccines will evolve with them, senior White House adviser Andy Slavitt told CNN.

"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 on Thursday.

The US has witnessed a 26% decline in new cases from this time last week, continuing the trend of the steepest decline in new cases since the start of the pandemic, according to data from Johns Hopkins University.

But variants, many of which appear to be more transmissible, have been spreading, with more than 1,500 cases reported in the US, according to the US Centers for Disease Control and Prevention.

Officials have been racing to administer vaccines quickly to get ahead of further mutations, with about 57.7 million doses administered so far across the country, according to the CDC.

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 said that does not mean that people should avoid the second shot.

"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."

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

Vaccination delays caused by harsh winter weather gripping much of the US means that many people will have to work "double time" to get back on track, according to Dr. Anthony Fauci.

"It's been slowed down; in some places going to a grinding halt," Fauci, the nation's top infectious disease expert, said in an interview with MSNBC on Thursday.

A number of states have reported delays in vaccine deliveries and distribution, forcing providers to cancel or reschedule appointments for vaccinations. The Federal Emergency Management Agency (FEMA) on Thursday said more than 2,000 vaccine sites are in areas suffering from power outages.

Fortunately, none of the vaccines that need to be stored at specific temperatures have been spoiled this week to officials' knowledge, Slavitt said.

Houston, hit with both power outages and water problems during the storm, plans to resume giving vaccinations Saturday and Sunday, the city's health department said in a release Thursday.

Many states hit early in the storms, particularly Texas, had to cancel vaccination appointments due to dangerous road conditions and power outages.

But Connecticut Gov. Ned Lamont said Thursday that so far the state has not had to make any cancellations.

"Look, there are disruptions," said Lamont. "Fortunately, we've got almost all our doses for this week and so far so good, no cancellations are anticipated but time will tell."

Black and Hispanic people are getting fewer vaccinations

The World Health Organization will launch a new declaration Friday, focusing on vaccine equity, Director General Tedros Adhanom Ghebreyesus said during a news briefing Thursday.

While Tedros' declaration will focus on vulnerable groups and small island states with less bargaining power than larger countries, inequity has already been a factor in the US.

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 smaller shares of vaccinations compared to their shares 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.

Researchers found higher rate of infection in pregnant women

Researchers of a study released Tuesday suggested that pregnant people should be prioritized for vaccination after they found that the COVID-19 infection rate among expectant women in Washington state was 70% higher than in adults of similar age in the state.

The infection rate in pregnant women in the study was 13.9 out of every 1,000 deliveries, compared to an overall rate of 7.3 out of 1,000 for 20 to 39-year-olds in the state.

The higher infection rates "may be due to the overrepresentation of women in many professions and industries considered essential during the COVID-19 pandemic — including healthcare, education, service sectors," lead author Dr. Erica Lokken said in a news release.

"Pregnant women are written out of the allocation prioritization in about half of U.S. States. Many states are not even linking their COVID-19 vaccine allocation plans with the high-risk medical conditions listed by the [Centers for Disease Control and Prevention] —which include pregnancy," Waldorf said.

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, UK 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.