COVID-19 vaccinations at State Farm and Phoenix Municipal stadiums have passed the 200,000 mark.
But as the U.K. variant B.1.1.7 strengthens its foothold, the need for vaccinations and precautions grows more urgent.
Arizona State University's Biodesign Institute has verified more cases of the faster-spreading variant, which also may alter the effectiveness of some vaccines, although Pfizer and Moderna appear to protect against it.
Biodesign Director Joshua LaBaer said continuing mutations underline the need to increase precautions and vaccination rates.
"The amount of vaccination that we've done in this state is tiny compared to the number of people in the state, even though we're making great headway," LaBaer said.
Models by the Centers for Disease Control and Prevention predict B.1.1.7 could become the dominant strain in the U.S. by March.
"This is a very transmissible variant. It gets around very quickly. And if it starts to get a foothold here in Arizona, then we could see rising numbers," said LaBaer.