New state data shows vaccination rates are at the lowest they've been since vaccines became readily available, with younger people least likely to be vaccinated.
A CDC report released this week shows young adults nationwide are losing interest in the shots, a concerning trend as the Delta variant continues to spread.
According to state numbers, vaccination rates among all age groups have dramatically slowed down since the vaccination peak.
In adults 65 and older, nearly 86% have received at least one dose, compared to 20-34-year-olds at 42% vaccinated and those under 20 at only 12.5%.
"The same thing that's happening in the country is happening in Arizona -- younger population meaning less than 30 years old, are reluctant to get the vaccine," said Dr. Ricardo Correa, an endocrinologist at the University of Arizona College of Medicine-Phoenix.
Dr. Correa said reasons for hesitancy vary among culture, race and ethnicity, but overall, younger adults don't perceive COVID-19 as a serious threat.
"Another thing I hear a lot is they don't trust in the vaccine because it was produced very fast, it can affect my DNA, my fertility, a lot of myths happening on social media that are spreading very fast. This is not true," he said.
TGen's Dr. Dave Engelthaler has been tracking variants in Arizona and said the Delta variant made up about six percent of our cases so far this month. He expects that to rise.
"It looks like the Delta variant might actually be the fittest, the one that spreads the fastest," said Dr. Engelthaler.
Experts worry Delta will soon become the predominant variant. It's more contagious and could lead to outbreaks among those not vaccinated. The nation's top infectious disease physician, Dr. Anthony Fauci, said it may already account for one in every five infections nationwide.
"Every time you have a transmission, you have an opportunity for a new mutation to occur and therefore a mutation might allow the virus to start to evade the vaccine or maybe cause more serious illness," said Dr. Engelthaler.
Right now, those vaccinated are protected against all variants of the virus.
Dr. Correa said in the Valley, hesitancy is most common among underserved communities, and there's been a big push to get Latinos vaccinated.
Experts say if more people don't get the shots, COVID-19 could be around for the foreseeable future.