(CNN) – The US Centers for Disease Control and Prevention (CDC) now considers the delta variant of the novel coronavirus, also known as B.1.617.2, a “variant of concern.”

The worrying alternative is given to strains of the virus that scientists believe are more transmissible or may cause more serious disease. Vaccines, treatments, and tests that detect the virus may be less effective against the worrisome variant. Previously, the CDC considered the delta variable to be of interest.

The CDC said the delta variant, first identified in India, shows increased transmissibility, a possible decrease in neutralization by some monoclonal antibody therapies under emergency clearance, and a possible decrease in neutralizing sera after vaccination in Laboratory tests.

The World Health Organization The delta variable was classified as a variable of concern on May 10.

Cases of Covid-19 have fallen in recent months in the United States, but there are fears that it may change as the pace of vaccinations slows and the spread of variable delta spreads. The Center for Disease Control They estimate it represents 9.9% of cases in the United States as of June 5.

At a COVID-19 briefing at the White House last week, Director of the National Institute of Allergy and Infectious Diseases, Dr. Anthony Fauci, encouraged everyone to get vaccinated against COVID-19, noting that the delta variant was in circulation in the United States. The United States at a rate similar to the inflection point observed in the United Kingdom, where the variable now predominates.

“We can’t allow that to happen in the US,” Fauci said, describing the UK experience as a “strong argument” for vaccination.

The variant is thought to be responsible for the most recent increase in cases in the UK and a case study in Scotland Published on Monday, it was found to be associated with nearly twice the risk of hospitalization compared to an alpha variant, B.1.1.7, which was first identified in the UK.

The United Kingdom announced on Monday that the easing of coronavirus restrictions will be delayed for another four weeks, until July 19, after an increase in cases and, in particular, the increased spread of the delta variant.

Delta variable in the United States

As of Sunday, the delta variant was responsible for about 10.3% of COVID-19 cases in the United States, according to Dr. Eric Topol, founder and director of the Scripps Research Translational Institute, who outbreak Variables were tracked throughout the epidemic.

It may not seem like much, but the speed at which it spreads is a concern.

“It doubles every seven to 10 days, which means when it arrives three weeks from now, this variant will be dominant,” Topol said. “This means we have two to three weeks to work on vaccination to stop this trend.”

In general, vaccines seem to keep variables in check. The alpha strain, for example, has been the dominant strain in the United States since late April. But with exceptions like Michigan, it hasn’t caused sudden spikes in cases in much of the country.

Topol said the US was able to “raise the stakes” and go “a complete explosion in vaccination” when the alternative arrived in the US.

With the delta variant, Topol is not too optimistic.

“This is by far the most worrisome type, because it’s 60 percent more contagious than alpha, so it’s a super prevalent strain,” Topol said. But the vaccination rate is stagnating.

While 43.9% in the United States are fully vaccinated, according to the Centers for Disease Control and Prevention (CDC), the rate at which people are vaccinated has slowed.

In Mississippi, approximately 29% of the population is fully vaccinated. In Alabama it is less than 31%. In Arkansas, it’s less than 33%. In Louisiana, Georgia, and Wyoming, the proportion is less than 34%, according to data from the Centers for Disease Control and Prevention (CDC).

Vaccines and Variable Delta

The good news is that people who have been fully vaccinated appear to have strong protection against the delta variant.

A study was published in scalpel She found that one dose of the covid-19 vaccine was not enough, but after the second dose, Pfizer/BioNTech offered 79% protection against the delta variant. That compares to 92% protection against the alpha variant.

else analyzing Public Health England found that two doses of the Pfizer vaccine appeared to be 96% effective against hospitalization.

Dr. Peter Hotez, director of the Vaccine Development Center at Texas Children’s Hospital, said Tuesday on CNN’s “New Day” that he is “extremely concerned” about the delta variant, even though it appears that two doses of the COVID-19 vaccines are working. Pfizer or Moderna is “very well” to protect against.

Now is the “tipping point,” Hotez said, recalling the surge in coronavirus cases across the South last year, when a “horrific” wave of cases surfaced in July and August.

“I have to believe that with this new variant of Delta, the same thing will happen again with anyone who has not been vaccinated or has only one dose of the vaccine,” he said. “And this is the time to get everyone vaccinated, because even if you want to vaccinate yourself or your teen tomorrow, it takes five to six weeks to get two doses of the vaccine and then another week later.”

CNN’s Naomi Thomas contributed to this report.