The Centers for Disease Control and Prevention has recommended that when the H1N1 flu vaccine is ready, the first people to get it should be children and young adults between age 6 months and 24 years. That strategy is expected to result in 59 million swine flu cases, 139,000 deaths and cost $67 billion.
But there is a better way, according to researchers from Yale and Clemson universities.
If vaccine doses were first distributed to children between age 5 and 19 and to adults age 30 to 39, there would be 15 million fewer infections and 31,000 fewer deaths, write mathematician Jan Medlock and epidemiologist Alison Galvani in Friday's edition of the journal Science. Their strategy would also save $14 billion, they calculate.
In their mathematical model, Medlock and Galvani assume H1N1 will be deadlier than the 1957 flu pandemic but tamer than the 1918 pandemic. They also assumed that each person infected with H1N1 will spread the virus to 1.4 additional people (if they are unvaccinated), as has been previously estimated.
To gauge how H1N1 will spread, they examined patterns in 97,904 personal interactions recorded by 7,290 people in a single day. That data led them to conclude that the strongest mixing occurs among people of similar ages, followed by mixing between school-age children and people in their parents’ age group. And children are known to be “responsible for a disproportionate amount of influenza transmission,” they write in their study.
All of that led Medlock and Galvani to conclude that the most important groups to immunize are 5- to 19-year-olds and their parents, typically between the ages of 30 and 39. This “optimal” vaccination strategy would require 62 million to 63 million doses of vaccine.
U.S. health officials have said 45 million doses will be ready by Oct. 15, with an additional 20 million doses coming online each week after that. It is not yet clear whether people will need one or two doses to get full protection.
The CDC will study the paper, but spokesman Tom Skinner told Nature News that he didn’t expect the public health agency to rethink its strategy.
“Our immunization recommendations really are not based on one single model,” he told Nature. “Models are based on many assumptions. They can be a helpful tool for identifying possibilities, but it’s really not possible to know how any specific model might play out.”
-- Karen Kaplan
Photo: Marisa Grunder got an H1N1 flu shot last week as part of a clinical trial, but at age 27, she is not considered a member of one of the high-risk age groups, according to a new study in Science. Photo credit: David Greedy/Getty Images