An aggressive vaccination program that first targets children and ultimately reaches 70 percent of the U.S. population would mitigate pandemic H1N1 influenza that is expected this fall, according to computer modeling and analysis of observational studies conducted by researchers at the Hutchinson Center's Vaccine and Infectious Disease Institute.
Published in the Sept. 11 issue of Science Express, the early online edition of the journal Science, the study—which includes the first estimate of the transmissibility of pandemic H1N1 "swine" flu in schools—recommends vaccination first for:
These groups include health care and emergency services personnel and those at risk for medical complications from pandemic H1N1 illness such as persons with chronic health disorders and compromised immune systems. Two doses of vaccine, delivered three weeks apart, may be needed to confer adequate protection to the virus.
Corresponding author Dr. Ira Longini and colleagues emphasized that a combination of factors—the availability of an effective vaccine to protect people against pandemic H1N1, coupled with the timing of the outbreak—will determine how quickly the pandemic can be slowed. The researchers estimate that to bring the pandemic under control aggressive vaccination of the population must begin at least a month before it peaks, concentrating on children as much as possible.
“Our estimates of pandemic H1N1 in households, schools and in the community places this virus in the higher range of transmissibility,” said Dr. Yang Yang, first author of the paper and a staff scientist at VIDI.
Although social distancing and the use of antiviral medicines can be partially effective at slowing pandemic flu spread, vaccination remains the most effective means of pandemic influenza control, the authors conclude. From a cost-effectiveness measure, vaccination remains the most effective, while closing schools and other social gathering places is the least cost-effective.
Vaccination increases population-level immunity and lowers the effective reproductive number of the virus, which results in two main effects: slowing the spread of infection and reducing the height of the pandemic peak; and reducing the overall illness attack rate, hospitalizations and mortality.
Other key findings in the study:
Longini and colleagues are considered among the world’s leading disease modeling experts. They are part of the federal government’s Models of Infectious Disease Agent Study Network, an effort funded by the National Institute of General Medical Sciences at the National Institutes of Health.
Funding for the study came from the National Institute of General Medical Sciences and the National Institute of Allergy and Infectious Diseases.