Masks and vaccinations will not be required at the Minnesota State Fair this summer, but both are encouraged to limit coronavirus transmission during the 12-day event.

While fair leaders weighed mandates in the face of a growing COVID-19 wave, they envisioned enforcement problems and opted for a voluntary approach because the mostly outdoor environment reduces transmission risks anyway.

"We are urging you to pitch in and do what's right. Particularly if you go inside, simply put a face covering on for the time you're shopping or visiting an exhibit," the fair stated in a Wednesday update.

Coronavirus infections have increased this summer despite 69.3% of eligible people 12 and older receiving at least first doses of vaccine in Minnesota. The positivity rate of COVID-19 testing has risen above Minnesota's 5% caution threshold, and COVID-19 hospitalizations in the state have increased from 90 in mid-July to 461 on Tuesday.

Masks will be required on buses to and from the fair and at first-aid stations. They also will be required for unvaccinated individuals on fair trolleys. They are recommended indoors and in crowded outdoor locations for people older than 2 who are medically able to wear them.

Visitors should consider weekdays when attendance is lower to reduce close contacts, said Jerry Hammer, the fair's general manager. Attendance usually exceeds 100,000 on the first Monday but 250,000 on the final Saturday. The fair is debuting an online Gopher Gauge that people can check for crowd levels.

The fair has seen more than 2 million visitors and record attendance in recent years, but it was canceled last year. Hammer said he doesn't expect as many people this year and the budget for the fair was based on attendance of 1.5 million.

Some attractions and thrill rides have been moved to reduce congestion that occurs only at peak times, Hammer said. The iconic photo "looking down the street and all you see is heads, it doesn't look like that most of the time, or it's the angle of the shot. You can actually walk through pretty easy."

The fair will host a COVID-19 vaccine clinic and offer masks at gates and info booths.

Gov. Tim Walz for months had promoted an unrestricted fair as motivation for mask-wearing and vaccinations to reduce COVID-19 levels. Hammer said cancellation wasn't considered despite the emergence of a fast-spreading delta variant of the coronavirus that is showing a slightly higher rate of infecting even fully vaccinated individuals.

Three studies published Wednesday by the Centers for Disease Control and Prevention showed that the Pfizer and Moderna vaccines maintained strong protection against COVID-19 hospitalizations and severe illnesses, but two of them showed a drop in vaccine effectiveness at preventing infections.

The findings matched an analysis last week of vaccine effectiveness in Mayo Clinic patients in Minnesota, but researchers stressed that the vaccines were approved to prevent severe illnesses and are achieving that goal.

Hennepin County Medical Center contributed to one of the studies, showing that the two-dose vaccines protected against COVID-19 hospitalizations after 24 weeks. Dr. Heidi Erickson, a co-author, said she is pleading with unvaccinated people to get shots based on her patients in intensive care.

"We're having patients with life-threatening disease in their late 20s and 30s. They're younger, most of them are previously healthy, and all of them are unvaccinated," she said.

Third Pfizer and Moderna shots have been authorized for immunocompromised people who didn't gain adequate protection from the first two. Federal authorities on Wednesday recommended booster doses for others starting Sept. 20.

Studies have been lacking on effectiveness of the Johnson & Johnson vaccine, which was approved for use weeks after the first two versions, and on whether its recipients will need boosters as well.

J&J vaccine has been given to only 274,000 of 3.2 million recipients in Minnesota — including Walz — but has been a key part of the state's strategy because it requires only a single initial dose and uses an established form of vaccine delivery that reduces concerns for some skeptics.

J&J and Pfizer doses will be part of a pop-up clinic this Saturday at U.S. Bank Stadium where adult recipients will enter a drawing for Vikings-Packers tickets and the first 100 recipients will receive autographed mini helmets.

The increased risk of breakthrough infections because of the delta variant prompted the CDC to recommend mask-wearing in K-12 schools and counties with substantial or high transmission rates — a level that exists in 82 of Minnesota's 87 counties.

Schools and businesses might be able to enforce mask-wearing, but Hammer said he doubted he could find anyone interested in jobs at the fair policing such a volatile and politically charged issue.

"The reality is we are having a challenge getting people to work the fun jobs," said Hammer, but he stressed that workers and volunteers are expected to set an example and wear masks.

The lack of a requirement could deter some fairgoers. Cameron Murray, 62, of Stillwater, discussed the fair with vaccinated friends and he said none planned to go without masks or vaccine mandates.

"I am not sure how sick I might get. I have some pre-existing conditions," he said. "But I might pass it onto others, and that is a risk I am not willing to take."

COVID-19 testing is encouraged three to five days after attendance at large events. The Minnesota Department of Health identified outbreaks involving three or more people last month at 13 fairs, four concerts and eight weddings.

The state on Wednesday reported five COVID-19 deaths and 1,163 infections, raising the state's pandemic totals to 7,742 deaths and 630,512 infections.