Last updated 6:30 p.m. Eastern
More than 22 million doses of H1N1 flu vaccine are available now, and most Americans should soon find it easier to get their dose, U.S. health officials said Tuesday.
"We're beginning to get to significant increases in the availability," said Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, at a briefing.
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Last week there were just 14 million doses on hand, despite predictions that as many as 120 million doses would be ready by mid-October. The slow supply trickle has frustrated Americans, who have stood in line for hours in some parts of the country.
The shortage has probably increased demand, Frieden said.
"It's quite likely that that too little vaccine is one of the things that's making people more interested in getting vaccinated, frankly. When we have shortages, we see an increase in demand," he said.
The vaccine is grown in eggs in a reliable but slow process, and smaller amounts of it were being produced per egg than expected. There were other snags, too, but health officials say manufacturers have overcome most of those and are making the vaccine more speedily.
The government has ordered 225 million doses.
A county-run public health clinic represents the end of what's so far been a sparse and slow-moving supply chain of the vaccine, reports CBS News correspondent Jeff Glor from New Jersey.
The beginning of that chain is when the CDC is told - every day - how much vaccine is available. That news that comes from McKesson, the massive health care company charged with national distribution, Glor reports. The CDC plugs that information into a computer program that determines how much can be given to each individual state - distribution based entirely on population, not on the spread of the illness.
As for the states?
"The CDC provides us on a daily basis the actual number, the balance of our doses that are available to us," said Dr. Tina Tan of the N.J. Health Department.
New Jersey then distributes vaccine to its 21 counties based on their populations, Glor reports. So far, Middlesex County has ordered 250,000 doses of vaccine for its 25 towns and 800,000 people. They've received only 10,000.
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CDC officials estimate that the H1N1 flu (also called swine flu) virus, first identified in April, has killed at least 1,000 Americans and caused at least mild illness in many millions of others.
The pandemic started in a frightening burst of cases in certain parts of the country, including New York, Boston and parts of the Southwest. Illnesses diminished somewhat in the summer and then began increasing across the country as schools reopened roughly two months ago.
H1N1 flu cases are waning in Georgia and some parts of the country lately, but still increasing in others. Health officials say it's hard to predict what will happen in the next few months.
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Among those who may need the vaccine most , as CBS News medical correspondent Dr. Jennifer Ashton reported Monday.
As H1N1 vaccine clinics have started to spring up, some pregnant women are choosing to line up.
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