ATLANTA, Georgia (CNN) -- With 46 states now reporting widespread H1N1 flu activity, more vaccine is slowly trickling out for those who want it.
According to the Centers for Disease Control and Prevention, 16.1 million doses of H1N1, or swine flu, vaccine had been made by Friday -- 2 million more than two days earlier. About 11.3 million of those had been distributed throughout the United States, according to CDC Director Dr. Thomas Frieden.
"We are nowhere near where we thought we would be," he said, acknowledging that manufacturing delays have contributed to less vaccine being available than expected. "As public health professionals, vaccination is our strongest tool. Not having enough is frustrating to all of us."
Frieden said that while the way vaccine is manufactured is "tried and true," it's not well-suited for ramping up production during a pandemic because it takes at least six months. The vaccine is produced by growing weakened virus in eggs.
In California's Los Angeles County, where the Department of Health was holding its first free H1N1 flu clinics Friday, distributing some 2,500 vaccinations, hundreds of people waited for hours, with some getting in line as early as 4 a.m.
Since the H1N1 flu pandemic began in April, millions of people in the United States have been infected, at least 20,000 have been hospitalized and more than 1,000 have died, Frieden told reporters in a news conference.
He said that having 46 states reporting widespread flu transmission is traditionally the mark of the peak of flu season -- and to have the flu season peak at this time of the year is "extremely unusual."
While some people are searching for a flu shot, others are still wary about the safety of the vaccine, either because they feel production has been rushed or for other reasons.
Frieden said there's no reason to believe H1N1 vaccine is less safe than regular flu vaccine. He reiterated that the vaccine is manufactured the same way seasonal flu vaccine is produced.
The vaccine is manufactured by same companies using "the same factories, the same safeguards as the seasonal flu vaccine that has been used for more than 100 million doses each year for many years," he said.
If the pandemic had started a little earlier than in April, he added, the H1N1 virus would have been included in this year's seasonal flu shot.
--CNN's Traci Tamura contributed to this report
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