Purpose: A novel Influenza A (H1N1) virus is circulating globally. Public health officials are struggling with decisions about priority and effort to devote to a vaccine. We evaluated the projected effectiveness and cost-effectiveness of no vaccination versus vaccinating the population at four and six months.
Method: We developed a dynamic compartmental transmission model of A (H1N1) in a large U.S. city to estimate what fraction of the population might need to be vaccinated at four and six months. We also measured outcomes related to costs, infections, deaths, and quality adjusted life years (QALYs). We estimated the severity of A (H1N1) from recent reports, and effectiveness and costs from the literature and expert opinions. All parameter assumptions were tested in sensitivity analysis.
Result: Results were dependent upon assumptions, but vaccination appeared to be cost-effective. At an R0 of 1.5 (reproductive rate: 1.5 infections from the initial infected individual); vaccinating 40% of the population at four months ended the epidemic (defined as an effective reproductive rate ≤ 1), averted 5,400 deaths, and was cost-saving relative to social distancing alone without vaccination. If vaccination at four months was not feasible, vaccinating 28% of the population at six months ended the epidemic, averted 3,400 deaths, and was cost-saving relative to social distancing alone without vaccination. Cost-effectiveness of vaccination was sensitive to several parameters, such as the reproductive rate. If the virus spread so quickly that the pandemic wave had died out in four or six months, then the intervention was no longer cost-effective. The value of vaccinating early was potentially large. If a city the size of New York could accelerate vaccination to start in four versus six months, and were willing to pay $50,000/QALY, it would be worth up to two billion dollars to vaccinate earlier.
Conclusion: Although it is challenging to prepare for vaccination against a novel influenza virus and it is uncertain how necessary or efficacious a vaccine will be, it appears to be effective and cost-effective to vaccinate for Influenza A (H1N1). In addition, the entire population would not need to be vaccinated in order to induce herd immunity and stop the pandemic. It would also be valuable to accelerate vaccine production from six to four months, to the extent that this is possible.
Candidate for the Lee B. Lusted Student Prize Competition