MONDAY, Oct. 5, 2009 (HealthDay News) -- To minimize deaths from the H1N1 pandemic swine flu, vaccination should start as soon as possible, a new U.S. study suggests.
"Earlier -- October versus November -- vaccination saves more lives and costs less," said the study's lead researcher, Dr. Nayer Khazeni, from the division of pulmonary and critical care medicine at Stanford University Medical Center.
"We find that vaccinating 40 percent of the population in October would decrease viral transmission and shorten the pandemic," she said.
Distribution of an injectable H1N1 vaccine started on a small scale this week, according to the U.S. Centers for Disease Control and Prevention.
Although most cases of the H1N1 flu are mild or moderate, close to 1,000 flu-related deaths occurred from August to September, and the flu season is just getting under way.
For the study, which is in the Oct. 6 issue of Annals of Internal Medicine, Khazeni's team constructed a computer model of a hypothetical city like New York, which has 8.3 million residents. They found that vaccinating 40 percent of the people in October or 35 percent in November saves lives, cuts medical costs and shortens the pandemic, compared with later vaccination.
Vaccinating just 40 percent of the population in October would save 2,051 lives and $469 million. Vaccinating that number in November, would prevent 1,468 people from dying and save $302 million, compared with no vaccinations, Khazeni's group projects.
The H1N1 vaccine has not shown any severe side effects, but the researchers used a conservative model with side effects similar to those in the 1976 swine flu vaccination campaign as well as a more severe scenario, Khazeni said.
"In both those scenarios, vaccination would still save more lives than cause side-effect related deaths," she said.
U.S. health officials have said they expect 45 million doses of injectable vaccine to be ready by late October. Supplies will increase weekly, with 190 million doses by year's end. There is no way to know if enough people will get their shots in time to maximize the life-saving and cost-saving benefits, researchers say.
Dr. Thomas A. Farley, New York City health commissioner and co-author of an accompanying journal editorial, said that "the benefit of this and other models is that they allow policymakers to weigh different policy decisions and test their potential impact."
But a limitation of models is that many real-world variables cannot be completely captured, which leads to uncertainty in the prediction, Farley said. "The greatest specific benefit of the Khazeni models is to demonstrate that, under some assumptions, early vaccination can greatly blunt an epidemic of influenza even if the vaccine efficacy is relatively low," he said.
Though the new H1N1 vaccine looks effective, it may be less effective than some other vaccines, Farley said. "One specific implication of this model is that, if we achieve high vaccination rates, this vaccine should have a very good population-wide benefit nonetheless."
Because initial shipments of the H1N1 vaccine are small, experts predict that most states will reserve early vaccination for children and for health-care workers, who will need to care for those who get sick. It's expected to be mid-October before inoculations are in full swing.
At the outset, doctors, clinics and drug stores won't have much notice of how many doses to expect, which will make advance scheduling difficult, experts predict.
In another flu study, Khazeni and colleagues applied the same modeling techniques to the virulent H5N1, or avian flu, virus. Their conclusion: The government needs to stockpile vaccines and antiviral drugs, such as Tamiflu, in preparation for potential outbreaks. This "is essential for future pandemics," Khazeni said.
"The H1N1 pandemic has been mild in many respects, but H5N1 and other viruses with pandemic potential exist, and we need to be prepared for a severe pandemic," Khazeni said.
For more information on H1N1 swine flu, visit Flu.gov.