TUESDAY, Oct. 13, 2009 (HealthDay News) -- While the majority of people hospitalized with the H1N1 swine flu have chronic medical conditions, many were healthy before coming down with the disease, a U.S. health official said Tuesday.
More than half of hospitalized adults had conditions such as asthma, chronic lung diseases, heart disease or immune system disorders, Dr. Anne Schuchat, director of the U.S. Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases, said during an afternoon press conference.
But, she added, "This virus can be serious even in people with no underlying conditions."
Among adults hospitalized with the H1N1 swine flu, 45 percent did not have a pre-existing medical problem and 6 percent were pregnant, Schuchat said. Among hospitalized children, 5.8 percent had sickle anemia or another blood disorder, she said.
"The most common underlying conditions [for children] were asthma and chronic lung disease, neuromuscular diseases and sickle cell or other blood disorders," Schuchat said.
The findings were based on data collected on 1,400 hospitalized adults and more than 500 hospitalized children whose medical centers participate in the CDC's Emerging Infections Program Network, she said.
As of last Friday, 12,384 people in the United States had been hospitalized with influenza since August and 1,544 had died, including 81 children, according to the CDC.
The number of pediatric deaths from the H1N1 swine flu is higher than usually seen with regular seasonal flu. During the past three years, deaths among children from the regular seasonal flu ranged from 46 to 88 annually, Schuchat said last Friday.
About 30 percent of the children who died had chronic medical conditions, such as asthma, cerebral palsy and muscular dystrophy. Among adults, about 30 percent died of severe bacterial pneumonia, she said Friday.
Schuchat said Tuesday that 9.8 million doses of the H1N1 vaccine are available. "I am happy to say that about half of the vaccine that's available for order is now the injectable form," she said.
The first batches of the vaccine were in a nasal spray called FluMist. Because FluMist is a live vaccine, it's only recommended for healthy people between the ages of 2 to 49 years old, and not for pregnant women, Schuchat said.
Schuchat said the availability of the H1N1 vaccine will continue to grow and ample supplies should be on hand by the end of October and early November. The CDC has been saying for some time that it anticipates having 40 million doses by the end of October and 190 million doses by year's end.
"Pregnancy and underlying conditions are ones that we highlight as recommended to receive the H1N1 vaccine when it becomes available in communities," she said.
Asked why pregnancy seemed to be a risk factor for complications from the H1N1 swine flu, Schuchat said: "There are probably two factors that influence the risk that pregnant women have for influenza complication. And this applies to both seasonal flu and the H1N1 flu. In pregnancy, there's a change in the immune system which makes it easier for the woman to hold the fetus and not have an immune reaction to the baby. And so risk of infections can be greater.
"The second issue," she added, "is probably more mechanical, that as the woman gets larger with the baby growing, there can be pressing on the airways and really a restrictive lung disease. So it's harder to take a deep breath and it's harder to fight off a lung infection especially in the later stages of pregnancy."
As for the regular seasonal flu, Schuchat said 77 million doses of that vaccine have been shipped. Although some parts of the country are seeing shortages of the vaccine, those shortfalls are expected to be temporary, with large quantities of the vaccine available in late October and November.
Since the seasonal flu season hasn't started yet, there's plenty of time to get a seasonal flu shot, even into December, Schuchat said.
For more on the H1N1 flu, visit the U.S. Centers for Disease Control and Prevention.