* U.S. securing vaccine supply ahead of immunizations
* Pregnant women, health workers likely get first shots
* CDC presumes vaccination to start mid-October
ATLANTA, July 29 (Reuters) - The U.S. government has taken delivery of 20 million doses of a vaccine against the new pandemic H1N1 swine flu, and should be ready to start an immunization campaign in October, officials said on Wednesday.
Vaccine advisers meeting in Atlanta may follow World Health Organization guidelines that put healthcare workers, pregnant women and patients with asthma and diabetes at the front of the line to get vaccinated.
The Advisory Committee on Immunization Practices may also examine ways to manage a complicated U.S. flu season, with people getting seasonal influenza immunizations alongside swine flu vaccines.
Robin Robinson of the U.S. Department of Health and Human Services told the meeting the government has contracted to buy around 200 million doses of vaccine and that 20 million have been delivered.
Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention said it still was not clear when vaccination could begin. But she told the meeting, “We want people to plan as though we will be able to go in mid-October.”
Data from human trials of the new vaccine, which have just begun, will not be available until late September, officials told the meeting.
H1N1 swine flu is now so widespread that the World Health Organization has stopped counting individual cases. Health experts are afraid it could worsen, especially when the Northern Hemisphere’s influenza season starts in the autumn.
Five companies are making H1N1 vaccine for the U.S. market -- AstraZeneca's AZN.L MedImmune unit, Australia's CSL Ltd CSL.AX, GlaxoSmithKline Plc GSK.L, Novartis AG NOVN.VX and Sanofi-Aventis SA SASY.PA.
It is not clear how much vaccine is going to be available. Some companies have reported this particular virus does not grow well in eggs, limiting the yield.
Most experts agree that people are likely to need two doses of H1N1 vaccine to get full immunity because very few have been exposed to the virus. That means the United States needs 600 million doses.
So the advisers must decide who will be vaccinated first while manufacturers work to make more vaccines.
Pregnant women may be near the front of the line. A report published earlier on Wednesday showed that pregnant women were four times more likely than others to have serious illness from H1N1 -- requiring long hospital stays - or to die. [ID:nN29265188]
The CDC’s Dr. Denise Jamieson said the most recent figures show the death rate is about 6 percent in pregnant women, who make up just 1 percent of the population.
Dr. Wellington Sun of the U.S. Food and Drug Administration said the agency was working with companies to find the quickest and best way to license an H1N1 vaccine for use. The easiest route would be to make the new vaccine supplemental to the annual seasonal flu vaccine, he said.
But this would require keeping the same ages and dosing regimen as seasonal flu -- which is given as one dose, and with preference to the elderly and people with chronic conditions.
H1N1 appears to spare the elderly more, and affects many previously health young adults and older children, unlike seasonal influenza.
Writing by Maggie Fox in Washington, editing by Vicki Allen
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