Elderly Americans who are used to being among the first in line for seasonal flu vaccines have been left off of the list of those who will have priority for swine flu shots this fall.
Instead, pregnant women and young people will be among those who go to the head of the line.
Health officials met at the Centers for Disease Control and Prevention in Atlanta today to decide whether the government should go ahead with mass vaccinations and who would get first dibs on a vaccine that could become available this fall.
Watch "World News With Charles Gibson" tonight at 6:30 ET for the full report.
After wrestling with which groups should get priority, the committee ultimately decided by a vote of 13 to 1 to give immunization priority to a group including pregnant women, those who care for infants under six months of age, health care and EMS workers, children and teenagers between ages 6 months and 18 years old, and anyone under the age of 64 underlying medical conditions.
Senior citizens will also have to wait behind 19 to 24 year olds, who often get sick in large numbers at college, but don't tend to get deathly ill.
The groups getting prioritized make up about half of the U.S. population.
According to the latest CDC numbers, more than 43,700 cases of swine flu have already been confirmed in the U.S. Fifty percent of those cases have been among people between the ages of 5 and 24. Just 1 percent of all the swine flu victims in recent months were 65 and older. The figures illustrate how different swine flu has been from regular flu, which is normally more dangerous for the elderly.
Of all cases in the U.S., more than 5,000 people have been hospitalized and 302 have died.
New Study Highlights Swine Flu Risks For Pregnant Women
The decision about vaccine priorities comes as a new study released this morning reveals that six pregnant women with swine flu died between April 15 and June 16 -- accounting for 13 percent of the total 45 U.S. deaths reported to the CDC.
All of them were healthy until they came down with the virus and developed pneumonia, according to the study based on CDC data. Not one of them received an antiviral to help them get better.
The study, published in the Aug. 8 issue of the British medical journal Lancet, indicates that pregnant women have been hospitalized more often, and have faced a higher risk of death, than other populations while battling the swine flu.
"If a pregnant woman suspects she has influenza, has influenza-like symptoms, the first thing she needs to do is call her health care provider and find out what she needs to do," Dr. Denise Jamieson, the study's author and medical officer in the CDC's division of reproductive health, said today. "And then the health care provider should have a system in place for triaging and evaluating pregnant women with influenza-symptoms promptly, and they should not hesitate to initiate antiviral therapy."
"I do think pregnant women should be a priority, right up there with health care workers," Tulane University's John Barry, author of "The Great Influenza," said Tuesday.
Yesterday others also considered who else should be on the list.
"Children and young adults with certain pre-existing medical conditions, and children, particularly younger children, should be included," said Dr. Andrew Pavia, chief of pediatric infectious disease at the University of Utah.
Others argued police, firefighters, the military, even utility workers, should also have priority.
"We don't want any of these people out in time of a national crisis," said Dr. Howard Markel at the University of Michigan.
Visit the ABC News OnCall+ Swine Flu Center to get all your questions answered.
Pregnant Women Vulnerable To Swine Flu
Any flu virus can be dangerous for a pregnant woman, but swine flu appears to be especially threatening.
The flu can be particularly dangerous in the second and third trimester of pregnancy, both for mother and baby.
That was the case for Kelly Tunstall, who was eight months pregnant when she developed flu symptoms. Tunstall was put in a medically induced coma in the hopes it would save her and her baby. Both she and her newborn survived.
"I found out that I had the swine flu after I had woken up from the coma," Tunstall told "Good Morning America." "The first thing I did when I woke up was I put my hands on my stomach and asked where my baby was, and was told that she was delivered by C-section. I was terrified that I had lost her and I didn't have my baby."
"I want every pregnant woman to know that if they have any kind of flu symptoms, push the doctor for a test," she said. "And if the doctor won't test them, insist that they treat them like they have the swine flu."
Dr. Jacques Moritz, director of gynecology at New York's St.Luke's Roosevelt Hospital, said Tuesday that a pregnant woman's weakened immune system makes her especially susceptible to the virus.
"What the body does, and what the baby does, really, is it sends out a message, 'Don't get rid of me,'" Moritz said. "So it brings down the immune system, so you don't reject the fetus."
He added, "Anybody that is going to be pregnant, in the second or third trimester during this upcoming flu season, should get vaccinated before, obviously, the flu season."
But pregnant women may be reluctant to receive vaccines, especially brand-new ones, while they're expecting. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, said on Tuesday it's "understandable" that pregnant women are hesitant to get vaccinated.
"That's a natural reflex, but you have to understand the balance of the risk of a vaccination," Fauci added.
"Unfortunately, the flu vaccine has been recommended since 2004 for any woman that's going to be pregnant during flu season, and yet we know that less than 15 percent of actually get vaccinated," Jamieson said. "So we do need to do a better job of ensuring pregnant women are vaccinated against influenza, both seasonal influenza as well as pandemic influenza."
Dr. William Schaffner, chairman of Vanderbilt University Medical Center's department of preventive medicine, advised pregnant women today that "The first thing you do is get vaccinated against the regular influenza and then stay alert when H1N1 vaccine becomes available, and get vaccinated then if that's the recommendation at the time."
He added on "Good Morning America" that between the regular seasonal flu and H1N1, "we may have a double barrel influenza season this year."
Mom-to-be Sivan Berman-Marciano said Tuesday she'll indeed opt for a swine flu vaccination if her doctor recommends it.
"If it's going to help not to have the swine flu and keep my baby safe, I will take it," Berman-Marciano said.
"I'm much more worried now than I was before getting pregnant because now, it's not only me, it's the baby also," she added.
The first American to die of swine flu was a 33-year-old pregnant woman in Texas. Her baby girl, delivered by caesarian, survived.
Near Seattle, 27-year-old Katie Flyte is fighting for her life after complications from swine flu. Flyte was six months pregnant and caring for her sick 2-year-old when she developed flulike symptoms that were misdiagnosed. She developed pneumonia, then respiratory failure, as doctors rushed to save her premature daughter.
"Go see your doctor," Katie's husband, Kenny Flyte, told KOMO News last week. "Don't even play around."
Meantime, in Australia, doctors are urging pregnant women to stay home during this swine flu season to avoid contact with anyone suffering from the illness. In Great Britain this fall there may be advice to pregnant women to avoid large social gatherings during the anticipatedpandemic.
GAO Report: Gaps Remain in Pandemic Flu Preparation
Today the GAO issued the latest in a series of warnings saying "gaps remain at all levels of government" when it comes to planning for a possible pandemic flu. The House Homeland Security committee meets today to discuss the state of those preparations.
"Further actions are needed to address the capacity to respond to and recover from an influenza pandemic, which will require additional capacity in patient treatment space, and the acquisition and distribution of medical and other critical supplies, such as antiviral and vaccines," the GAO report said.
The latest numbers show that more than 43,700 cases of swine flu have already been confirmed in the U.S. Fifty percent of those cases have been among people between the ages of 5 and 24.
Of all cases in the U.S., more than 5,000 people have been hospitalized and 302 have died.
The CDC's worst case scenario is that if nothing is done, 40 percent of Americans could be infected over two years, and hundreds of thousands could die.
To prevent that, health officials are working hard to prepare a swine flu vaccine.
"The lights are on in the laboratories at night," Schaffner said today. "This is a race with the virus. We intend for that vaccine to get there first."
Clinical trials for a vaccination are expected to start in August, to be followed by a voluntary vaccine program.
Pediatrician Dr. Jim Rice and his wife have decided their four children will take part in the August tests.
"I'd like my kids to be protected," Rice told "GMA." "Being able to do this as part of a trial may help contribute to the greater good, to some extent, as well," he said.
After the tests, vaccinations were initially anticipated to begin mid-October, but at today's meeting there was some concern about whether that timeline will hold. Data from the trials may not be ready for scientists to review until the end of September, and it could take another four to six weeks to begin a vaccination program. That could mean the start of the vaccine program gets pushed back into November.
"What I heard was concern that we may not be ready by October," Kristin Ehresmann, chief of the Minnesota Department of Health's immunization, tuberculosis, and international health section, said today. "If we are not going to make October, tell us now."
Schaffner called mid-October "a little bit optimistic," adding, "Everyone is working very hard to get this vaccine out as quickly as possible, but it's going to be tight."
ABC News' Olivia Hallihan, Tom Shine and ABC News' Medical Unit contributed to this report.