MINNEAPOLIS -- Freezing temperatures may have ruined thousands of doses of vaccines, meaning patients may need new injections, but the clinic that gave the shots said no one was in danger.

About 3,400 people, half of them children, received the questionable vaccines from Park Nicollet Clinic in the Minneapolis metropolitan area. The vaccines included polio booster shots, hepatitis A and B shots and Prevnar, a vaccine for infants and toddlers.

There have been no signs of illness so far among the patients, though some probably weren't protected against disease, said Dr. Hal Martin, medical director of Park Nicollet's travel clinic.

The patients received their vaccines on days when temperatures in storage rooms fell below freezing. The vaccines are supposed to be kept at 35 to 46 degrees.

The problem came to light at a Park Nicollet clinic in suburban Minnetonka. A check of storage logs revealed the same problem at eight other Park Nicollet sites since December.

The same cold-storage problem has also been found at five or six other unidentified clinics in Minnesota, state epidemiologist Kristen Ehresmann said. It also has been happening around the country, according to the U.S. Centers for Disease Control and Prevention in Atlanta.

Park Nicollet said it was spending about $300,000 to correct the problem, including providing replacement shots.

Getting a second vaccine is safe, medical officials said. "It might cause a sore arm, but you cannot be overvaccinated," Martin said.

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On the Net:

Park Nicollet Clinics: http://www.parknicollet.com