# 3717
A study today that that gives us some numbers regarding the transmissibility of the novel H1N1 virus, and suggests that if a successful vaccination program could have been kicked off a couple of months sooner, we might have been able to mitigate the fall spread of the pandemic virus in the US.
First the abstract, followed by excerpts from the press release by the Fred Hutchinson Cancer Research Center, followed by a few comments.
The Transmissibility and Control of Pandemic Influenza A (H1N1) Virus
Yang Yang 1, Jonathan D. Sugimoto 2, M. Elizabeth Halloran 3, Nicole E. Basta 2, Dennis L. Chao 1, Laura Matrajt 4, Gail Potter 5, Eben Kenah 6, Ira M. Longini Jr.3*
Pandemic influenza A (H1N1) 2009 (pandemic H1N1) is spreading throughout the planet. It has become the dominant strain in the southern hemisphere, where the influenza season is under way. Here, based on reported case clusters in the USA, we estimate the household secondary attack rate for pandemic H1N1 to be 27.3% [95% confidence interval (CI) 12.2% to 50.5%].
From a school outbreak, we estimate a schoolchild infects 2.4 (95% CI: 1.8 to 3.2) other children within the school. We estimate that the basic reproductive number, R0, to range from 1.3 to 1.7 and the generation interval to range from 2.6 to 3.2 days.
We use a simulation model to evaluate the effectiveness of vaccination strategies in the USA for Fall 2009. If vaccine were available soon enough, vaccination of children, followed by adults, reaching 70% overall coverage, in addition to high-risk and essential workforce groups, could mitigate a severe epidemic.
And the Press Release.
Study find that vaccination of children and 70 percent of U.S. population could control swine flu pandemic
SEATTLE — Sept. 10, 2009 — An aggressive vaccination program that first targets children and ultimately reaches 70 percent of the U.S. population would mitigate pandemic influenza H1N1 that is expected this fall, according to computer modeling and analysis of observational studies conducted by researchers at the Vaccine and Infectious Disease Institute (VIDI) at Fred Hutchinson Cancer Research Center.
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 influenza in schools – recommends that 70 percent of children ages 6 months to 18 years be vaccinated first, as well as members of high-risk groups as identified by the U.S. Centers for Disease Control and Prevention.
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.
<SNIP>
Other key findings in the study:
• The current pattern of pandemic spread is most likely to be similar to the Asian influenza A (H2N2) pandemic of 1957-58. Substantial spread was expected to begin in early September with the epidemic peaking in mid to late October.
"In this case, child-first, phased vaccination would need to start as soon as possible, and no later than mid September to be effective for mitigation," said Longini, a biostatistician in the Center for Statistical and Quantitative Infectious Diseases at the Hutchinson Center. He is also a professor of biostatistics at the University of Washington School of Public Health. Longini said that the current U.S. plan called for the vaccination to probably start in mid October, which could still be effective if the epidemic peaked in November or December as it did during the Hong Kong influenza A(H3N2) of 1968-69.
It was never really in the cards that we could detect a novel virus in late April of this year, and manufacture and roll out a vaccine to 70% of the public before October.
Even if the vaccine could have been manufactured and tested by September, getting it into the arms of 200 million people would still represent an impossible obstacle.
Had the novel virus appeared earlier, or were we a lot further along in our conversion over to cell-based vaccine manufacturing . . . then perhaps it would have been possible.
While we are unlikely to do much to curb the fall wave of this virus with a vaccine, we may be able to quell a second winter or spring wave if we can get enough people inoculated over the next few months.
Novel H1N1 is likely to be with us for years, and so building herd immunity in our society has value, even if it comes too late for this fall’s wave.
Unknown of course, is whether, once the vaccine is available, we can actually get 70% of the population to take it.
