posted on Oct, 16 2009 @ 11:47 PM
Interesting tid bits-
We use data on confirmed cases of pandemic influenza A(H1N1), disseminated by the United States Centers for Disease Control and Prevention(US CDC), to
fit the parameters of a seasonally forced Susceptible, Infective, Recovered (SIR) model. We use the resulting model to predict the course of the H1N1
influenza pandemic in autumn 2009, and we assess the efficacy of the planned CDC H1N1 vaccination campaign. The model predicts that there will be a
significant wave in autumn, with 63% of the population being infected, and that this wave will peak so early that the planned CDC vaccination campaign
will likely not have a large effect on the total number of people ultimately infected by the pandemic H1N1 influenza virus.
The best-fit model is shown in Figure 2, with the influenza H1N1 data overlaid. The model predicts that the peak wave of infection will occur near
the end of October in week 42 (95% CI: week 39,43), with 8% of the population being infected during that week (95% CI: 6%,13%). By the end of 2009,
the model predicts that a total of 63% of the population will have been infected (95% CI: 57%,70%).
Figure 2. Model of the H1N1 influenza pandemic in the United States and prediction for autumn 2009
The most optimistic assumptions about the CDC vaccination campaign yielded a relative reduction of only 6% in the total number of infected
individuals. If we assume a 40% symptomatic infection rate, and a mortality rate of between 0.05% and 0.5%, this corresponds to an estimated
prevention of between 2,500 and 25,000 deaths. The actual reduction would certainly be lower because 10-30% of adults vaccinated will not achieve
immunity [7,8]. Also a large fraction of the population targeted by influenza A(H1N1) vaccinations are children.
Vaccination immunity in children develops at least four weeks after vaccination and would occur too late in the pandemic to make a significant
difference to the number of infected in that age group.
The cost benefit analysis involved in devising a pandemic influenza vaccination campaign is extremely complicated, especially due to the ever evolving
nature of the pandemic. What we learn from the successes and mistakes of vaccination programmes developed during the current H1N1 influenza pandemic
will greatly aid us in decision making during future influenza pandemics