Hospitals around the country are turning away visiting children and tightening restrictions on adults, too, in hopes of limiting the spread of the H1N1 flu in the hallways.

Utah and Colorado are recommending visitor limits for hospitals statewide. But mostly it's a hospital-by-hospital decision.

Some hospitals are trying education instead of rules, posting signs that urge people of any age to postpone that visit if they have a sniffle or cough. But there's little science the limits work.

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Consequently, neither the Centers for Disease Control and Prevention nor the American Hospital Association have set guidelines on the issue.

Dr. William Schaffner, a flu specialist at Vanderbilt University Medical Center, says you can't hermetically seal an institution.

"You can have people who are going to get sick tomorrow who already are excreting the virus," he said.

The H1N1 vaccine is in high demand as people try to protect themselves from the flu.

More than 2,600 people stood in line — sometimes longer than two hours — to be among the first in southern Nevada to get the injectable vaccine.

The Southern Nevada health district said they received more than 48,000 doses of the vaccine, including an initial delivery of 20,000 FluMist doses.

The Associated Press contributed to this report.