Pregnant women, healthcare workers and children six months to 18 years should be given access to H1N1 flu vaccinations first this fall, said the Advisory Committee on Immunization Practices, as well as parents and caregivers of infants, young adults between the ages of 19 and 24 and non-elderly adults who have high-risk medical conditions.
This target group was estimated by the CDC to include about 159 million people.
The U.S. government has ordered nearly 195 million doses of H1N1 flu vaccine from five producers for a possible fall vaccination campaign, but the government estimates that about 120 million vaccine doses will be available to the public by late October. The CDC said Wednesday it is likely that people will need two doses of the vaccine.
Dr. Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at the CDC said the supply may still be enough because only 20 to 50 percent of the population group recommended to get the seasonal flu vaccine actually get the vaccine.
"If we use seasonal influenza demand and uptake as our expectation we may have plenty of vaccine right off the bat," said Schuchat.
If the supply is available, the panel voted the recommendations should first be extended to non-elderly adults then to people 65 and older. While many strains of flu pose a significant health risk to the elderly, people in this age group seem to have higher immunity to this strain and have been "largely spared" by H1N1, according to Schuchat.
About 120 million doses of adjuvant, a compound that would stretch the number of doses of vaccine available from the active ingredient, have also been ordered by the government. Schuchat said the CDC is "evaluating the need for adjuvants" but said the CDC is "expecting not to need them" at this point.
Adjuvant is found commonly in European flu vaccines, but there are no licensed flu vaccines with the ingredient currently in the United States, reported the Associated Press.
The CDC has reported nearly 44,000 cases of H1N1 influenza and 302 related deaths in the United States. The World Health Organization declared H1N1 a pandemic in July and last week called it the fastest-moving pandemic ever. The group also said school-age children remain most affected by the virus.
U.S. human trials for swine flu vaccinations are slated to start within weeks -- last week the National Institutes of Health announced the sites for the trials and called for several thousand volunteers.
Saint Louis University's Center for Vaccine Development, the University of Maryland Medical Center, Baylor College of Medicine, Cincinnati Children's Hospital Medical Center, Emory University; Group Health Cooperative in Seattle, Washington, the University of Iowa and Vanderbilt University are among the vaccine trials sites.
Volunteers will be screened thoroughly and inoculated. After 21 days they will receive another dose.
If early results indicate the vaccines are safe, similar trials will begin with healthy children.
Preliminary data from the studies will not be delivered to the Food and Drug Administration until September, so a federal advisory panel has recommended that the FDA license a vaccine for the H1N1 flu virus before the safety data is released, reported DowJones.
But producing enough vaccine to meet the demand will remain a challenge even if the trials go well. The World Health Organization reported the strains of the virus being used to make vaccine are yielding less of the crucial vaccine antigen than normal.
Five companies are making H1N1 vaccine for the U.S. market -- AstraZeneca's MedImmune unit, Australia's CSL Ltd, GlaxoSmithKline Plc, Novartis AG and Sanofi-Aventis SA.
Novartis AG said in July they are harvesting one dose or less of the component they need from each egg in which the virus is grown-about a third to a half of the typical yield for a seasonal flu vaccine, reported Bloomberg News.
While the U.S. is hoping successful trials and production will allow for a vaccination campaign in October, other nations are pushing for a faster rollout.
The European Medicines Agency, the EU's top drug regulatory body, is accelerating the approval process for the vaccine and several countries, including Britain and France, have said once the vaccine is approved they will start using it within weeks.
At least 50 governments have placed orders or are negotiating orders with drug companies for H1N1 vaccine, reported Reuters.
The U.S. Centers for Disease Control and Prevention has also broadened its recommendations for seasonal flu vaccine in the last year, saying last week that all children over the age of 6 months should get one. Previously children and adolescents between 6 and 18 years old were not included in the recommendations.
Two U.S. flu vaccine makers have already started to ship seasonal flu vaccine to health providers in the United States in anticipation of a busy campaign for both the seasonal flu and H1N1 flu vaccines. The seasonal flu vaccine will not include the H1N1 vaccine, but the vaccine program may work in tandem.