GLENDALE, Ariz. (NewsNation Now) — Arizona is leading the nation with its COVID-19 infection rates and deaths, topping California where the population is quadruple in size.

Local researchers believe virus cases are on the rise despite more vaccinations.

“What we’re seeing in Arizona is small household groups, comfortable taking their mask off and being close to people that they don’t necessarily live with,” Dr. Cara Christ, Arizona Health Director said.

Dr. Christ runs Arizona’s Department of Public Health. She acknowledged the dire and deadly situation in her state, highlighting to NewsNation this week’s ramped-up efforts to vaccinate up to 6,000 Arizonans a day at State Farm Stadium.

“What we’re hoping that the increase from the holidays will be our high point and hopefully plateau. Vaccine is a very important component of that,” Dr. Christ said.

Despite thousands of shots available in the state, health researchers say the rate of infection remains greater than the rate of vaccination.

“The worst is yet to come,” Dr. Joe Gerald, University of Arizona, COVID-19 Modeling Team said.

Dr. Gerald said cases and deaths could possibly quadruple in the weeks ahead, negating the impact of vaccinating 2% of Arizona’s population so far.

“We’re actually getting far enough into this outbreak to where natural immunity is going to begin to come into play in a relatively short order, and we’re going to be nowhere near where we need to be with regard to vaccination,” Dr. Gerald said.

In a joint news conference Wednesday, Arizona’s top hospital leaders said the system is prepared for a worsening of the surge.

However, staffing is a factor.

“Our healthcare givers are very tired. They have been working nonstop since the beginning of 2020 to deal with all of the tragedy of the pandemic. So I would say the health system is very strained,” Dr. Stephanie Jackson, Honor Health Arizona.

Health officials estimate that one in 10 Arizonans are infected, with many of them asymptotic and unaware.

Even so, Dr. Christ defends the state’s pandemic approach.

“You know, California is on a significant lockdown and they’re still seeing increased numbers so we’re working on making sure our mitigation strategies are in place and making sure Arizonans can get vaccinated,” Dr. Christ said.

Arizona is among about a dozen states without a mask mandate.

The state death toll from COVID-19 topped 10,000 earlier this week. And just in the past two days, that toll has jumped to 10,673.