FRIDAY, Feb. 11, 2005 (HealthDay News) -- U.S. flu rates would drop dramatically if the majority of schoolchildren, as well as members of high-risk groups, were vaccinated every fall, a new study suggests.
"Children are the most responsible for transmission of the flu. So, by vaccinating children in large enough percentages -- over 50 percent -- you could shut off transmission [to much of the population] in quantifiable amounts," said Ira Longini, a professor of biostatistics at Emory University's Rollins School of Public Health.
The results of his mathematical model appear in the Feb. 15 issue of The American Journal of Epidemiology.
In an encouraging development, federal statistics released Thursday showed that 57.3 percent of children aged 6 months to 23 months of age were vaccinated from September through December 2004, the first year that influenza vaccination was added to the childhood immunization schedule. A 2002 survey showed that only 7.7 percent of children in the same age group were vaccinated for influenza, according to the U.S. Centers for Disease Control and Prevention.
"It is wonderful news that so many children are being vaccinated against a potentially life-threatening illness like influenza," said Dr. Julie Gerberding, CDC director. "We must continue to urge parents to vaccinate their children and urge those at high risk for serious complications from influenza to step up and get vaccinated because the shot can save lives."
Children who are aged 6 to 18 tend to transmit the flu virus more readily than any other group of individuals due to their exposure potential to each other and because they have less immunity than adults, Longini said. So, the more children who are vaccinated against the flu, the less likely overall transmission to the entire population, his study concluded.
Longini pointed to several earlier studies that found a significant drop in flu rates when a large-scale vaccination program was undertaken among schoolchildren. A community trial in Michigan in 1968 found that when 85 percent of schoolchildren were vaccinated against a type of influenza that year, there was a 67 percent drop in flu rates among all townspeople, compared to a neighboring community that did not conduct a child vaccination program, he said.
Similarly, the Japanese government vaccinated approximately 80 percent of schoolchildren each year against the flu from 1962 to 1987, preventing an estimated 37,000 to 49,000 deaths annually among the elderly, Longini said.
It was the weight of these studies, combined with the shortage of flu vaccine in the United States this season, that prompted Longini and his colleague, Elizabeth Halloran, to do their analysis.
"I thought, 'There's a better way to do this,'" he said.
Using mathematical models, Longini determined that if 60 percent of all U.S. schoolchildren between 6 and 18 were vaccinated, as well as high-risk seniors, the number of flu cases among children up to 18 years old would drop from 17 million to about 500,000. And, the number of deaths among those over 65 would fall from 34,000 annually to 6,600.
Longini said that while these figures are compelling, there are a number of reasons why there is no broad-based program to vaccinate schoolchildren each year.
"Not everyone accepts this idea. The thinking is that if you vaccinate someone, that's who you're protecting. But that's not true," he said. "Once you get enough people vaccinated up to a threshold level, the transmission drops dramatically" across the board.
Also complicating efforts, he said, is the question of allocation of health resources.
"Flu isn't perceived as a big problem," Longini said. "And the question is, should the resources be used for other things, like cancer?
Dr. Keith Powell, Noah Miller Chair of Pediatrics at Akron Children's Hospital in Ohio and a member of the American Academy of Pediatrics' infectious diseases committee, said the data from Longini's analysis is compelling. A comprehensive child flu vaccine initiative would be very cost-effective and should be studied further, he added.
"If we really want to stop transmission, we could do a better job," Powell said. "I would do a demonstration project in the United States, taking a few geographic areas and comparing morbidity and costs with those areas that don't have the vaccination project. And if the answers are as clear as the mathematical model, I would make it a policy."
There are about 60 million schoolchildren in the country, so 42 million doses would be needed to reach the threshold of a 70 percent vaccination rate among children, the optimal level, Longini said.
Longini said that if the federal government guaranteed the purchase of this amount of vaccine, manufacturers would step forward to produce it on an annual basis.
More information
The latest guidelines on flu vaccination can be found at the U.S. Centers for Disease Control and Prevention.
