THURSDAY, Aug. 20, 2009 (HealthDay News) -- The best way to stop the spread of flu, be it the seasonal flu or swine flu, is to vaccinate those most likely to spread the virus, namely school children and their parents, new research suggests.
These recommendations run counter to those of the U.S. Centers for Disease Control and Prevention, which call for targeting those most likely to develop complications from flu or die, say scientists at Clemson University and Yale University School of Medicine.
"If there is a moderate amount of vaccine available, the ideal thing to do is vaccinate schoolchildren and people their parent's age," said lead researcher Jan Medlock, an assistant professor in the department of mathematical sciences at Clemson. "This would then indirectly protect the rest of the population.
"Stopping the transmission in schools would then keep the kids from bringing it home to their parents, and keep their parents from giving it to co-workers, grandparents, whatever," he added.
The big difference between these recommendations and those from the CDC is that Medlock does not target children under 5. "Because they are not in school, they are not actively spreading the disease, so vaccines aren't being as well used as they could be used in another age group," he said.
In addition, unlike the CDC's recommendations, Medlock's do not include people over 50. "They can be better protected by stopping the transmission among school kids," he said.
The report is published in the Aug. 20 online edition of Science.
For the study, Medlock and Alison P. Galvani, an associate professor of epidemiology at Yale, created a mathematical model of how flu is transmitted that pinpoints the best strategy for distributing vaccines among age groups that would minimize the spread of the virus.
They based their model on data from past flu pandemics, taking into account deaths, infections, total years of life lost and economic costs. By comparing a theoretical outbreak today with the flu epidemics in 1918 and 1957, they argue that a flu epidemic in the United States could be stopped with about 63 million doses of vaccine.
This assumes that vaccines target children (aged 5 to 19), who are most responsible for spreading flu, and adults (aged 30 to 39), who get flu from their children. This strategy would help protect the remainder of the population from infection, Medlock and Galvani say.
Moreover, the 63 million vaccine doses in the model are less than the 85 million doses given each year in the United States for seasonal flu, they noted.
For seasonal flu, the CDC recommends that children aged 6 months to 19 get vaccinated as well as pregnant women, people 50 and older, people with certain chronic medical conditions, people living in nursing homes and other long-term care facilities, and people who live with or care for those at high risk for complications from flu.
Right now, the CDC is considering recommendations for whom should be vaccinated against the new H1N1 flu strain. Recommendations from the CDC's expert panel suggest targeting pregnant women, children 6 months and older and health-care workers first.
Dr. Marc Siegel, an associate professor of medicine at New York University Langone Medical Center in New York City, doesn't think that using historical data is a good method for predicting flu, but believes the researchers drew the right conclusions about vaccine use nevertheless.
"Their point is that children are super-spreaders, and adults are secondary spreaders, and I really agree with that," Siegel said. "I think their point about targeting spreaders and super-spreaders is right."
This use of vaccine builds what is called herd immunity, Siegel explained. "The best way to protect people that are most vulnerable is to vaccinate the spreaders," he said.
Another expert, Dr. Pascal James Imperato, distinguished service professor and chair of the department of preventive medicine and community health and director of the master of public health program at the State University of New York Downstate Medical Center in New York City, says the researchers correctly conclude that schoolchildren are often responsible for the transmission of influenza.
But they also conclude that the parents of infected children serve as bridges to spread the disease to others, Imperato said. "This latter conclusion only holds true if the parents are not already immune to the viral strain, either through vaccination or natural infection," he said.
There are frequent changes in the influenza strains that predominate in any given year, Imperato said. "Age-specific increased or decreased susceptibility to a given strain of influenza virus very much depends on the previous epidemiologic history of the strain," he noted.
"Annual age group-specific recommendations concerning vaccination against influenza need to be made on the basis of the history of the predominant strains of virus circulating," Imperato said. "As a result, these recommendations may vary from year to year and cannot be based on a statistical outcomes model that does not incorporate this and other very significant variables."
More information
For more information on flu, visit the U.S. Centers for Disease Control and Prevention.
