The Advisory Committee on Immunization Practices, a panel of medical experts from around the country that advises the Centers for Disease Control and Prevention recommended on Wednesday that five groups of people should be vaccinated first.

It would include people with the highest risk of complications and severe illness from the new H1N1 virus; pregnant women; people caring for infants under 6 months; children and young adults from 6 months to 24 years; and people aged 25 to 64 with medical problems like asthma, diabetes or heart disease.

The recommendations were issued at a meeting of the Advisory Committee on Immunization Practices, a panel of medical experts from around the country that advises the Centers for Disease Control and Prevention.

The U.S. government has taken delivery of 20 million doses of a vaccine against the new pandemic H1N1 swine flu , has ordered a total of 195 million doses and should be ready to start an immunization campaign in October, said Robin Robinson of the U.S. Department of Health and Human Services.

Data from human trials of the new vaccine, which have just begun, will not be available until late September, officials said.

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.

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