Colorado’s COVID-19 situation is getting worse, and one member of the state’s modeling team said that if you want to go back to the carefree days of early summer, it’s time to put on your mask.

Normal activities will become safe again when the vaccination rate is high and the number of new infections is low, said Beth Carlton, an associate professor of environmental and occupational health at the Colorado School of Public Health.

“We need to rely on more than just vaccines,” she said, noting that while they’re highly effective at preventing severe illness and death, breakthrough infections will increase when the rate of transmission is high like it is now.

The growth in both new cases and hospitalizations accelerated in the last seven days, meaning the current wave of infections will almost certainly pass the height of this spring’s fourth wave.

By one measure, it already has: 734 people were hospitalized with confirmed or suspected COVID-19 as of Monday afternoon, putting this wave behind only spring 2020 and fall 2020, when hundreds died each week.

The Colorado Department of Public Health and Environment reported 10,277 cases in the week ending Sunday, which was the highest total since the end of April. It was also a significant jump from the previous week’s roughly 7,800 cases.

The increase in cases isn’t just because more people got tested — the percentage of COVID-19 tests coming back positive is higher than it was last week, and well above the state’s 5% goal. The higher the positivity rate is, the more likely it is that the state doesn’t have a full picture of how many people are actually infected.

Colorado’s daily updates don’t specify how many infected people were not vaccinated, though Gov. Jared Polis referred to a “pandemic of the unvaccinated” in Monday’s statement touting the U.S. Food and Drug Administration’s decision to fully approved the Pfizer vaccine.

All but six Colorado counties had enough new cases, compared to their population, to reach the level where the U.S. Centers for Disease Control and Prevention recommends wearing masks in crowded indoor spaces. The exceptions were Bent, Conejos, Crowley, Jackson, Otero and Washington counties.

One number moving in the right direction was vaccinations, which rose for a fifth week in a row.

At least 67,000 people got shots in the week ending Saturday — a number that will almost certainly rise as the state finishes tallying all of the doses that went into arms. About two-thirds of eligible Coloradans (and 73% of Denver residents 12 and older) are fully vaccinated.