DETROIT (AP) — Michigan has expanded vaccine eligibility, a move that comes as public health experts voice fresh concerns about the state’s rising COVID-19 infection rate.

Residents age 50 and older are now eligible for vaccines. Ford Field in Detroit is set to open Wednesday as Michigan’s first federally run mass vaccine site.

However, the state’s COVID-19 cases have been increasing. Dr. Joneigh Khaldun, Michigan’s chief medical executive, said the state’s case rate spiked 77% over the past four weeks to 172.9 cases per million people.

“I am quite worried that we’re entering another surge,” Dawn Misra, a professor of epidemiology and biostatistics at Michigan State University’s College of Human Medicine, told The Detroit Free Press. “If you’ve been watching the numbers the last couple of weeks … you could just see it all coming.”

Michigan reported 3,730 new COVID-19 cases Friday, the most since Jan. 8, according to the newspaper. On Saturday, it reported 2,660 new cases, compared with 1,659 a week earlier. Overall, the state has confirmed nearly 16,000 COVID-19 deaths.