WASHINGTON (NewsNation Now) — Young adults are the least likely age group to be vaccinated, putting them at risk of contracting more contagious variants of COVID-19, the U.S. Centers for Disease Control and Prevention reported Monday.

“What we’re seeing is a lower rate among young people,” said White House press secretary Jen Psaki. “That’s concerning, especially with the Delta variant being on the rise as it is, which does not discriminate by age, which could still cause death, illness,”

Now identified in more than 40 states, the Delta variant is positioned to become the dominant coronavirus strain.

Dr. Peter Hotez, the dean for the National School of Tropical Medicine at Baylor College of Medicine, says unvaccinated young adults should not feel more protected against the virus than older populations because the new variants are different than the original strain.

“That’s your father’s COVID-19 and this has changed,” said Hotez. “These variants are different. They’re more transmissible and seem to produce fairly severe illness.”

Hotez explained people should expect children and teens in intensive care this summer.

Not only are young adults the least likely to get the shot in the country, but the CDC also says their weekly rate of vaccination is continuing to decline.

Some of the vaccine resistance has roots in politics — caused by outrage at Dr. Anthony Fauci, the nation’s top infectious disease expert, for changing mask guidance and recommending inoculation.

On Monday, Fauci hit back, calling the criticism against him “nonsense.”

“It is essential as a scientist that you evolve your opinion and your recommendations based on the data as it evolves, that is the nature of science,” Fauci said. “People who criticize me about that are actually criticizing science.”