University of Iowa Health Prediction Market
2007-08 Influenza Vaccine Effectiveness Market
Seasonal influenza is a major cause of morbidity and mortality throughout the world—an estimated 36,000 deaths and 120,000 hospitalizations occur annually in the United States alone. Unlike many viral diseases, a vaccine is available for seasonal influenza. However, the effectiveness of each season’s vaccine varies.
Influenza virus tends to undergo antigenic drift; therefore, every season the vaccine must be reformulated. Each season, vaccine effectiveness (VE) depends upon the degree to which the strains contained in the vaccine “match” the dominant strain of influenza circulating in the population. In seasons with well-matched vaccine, the influenza VE is expected to be between 70-90% successful among healthy adults less than 65 years of age. If a vaccine mismatch occurs, the morbidity and mortality for influenza may increase dramatically, especially in highly vaccinated populations. Information about vaccine effectiveness is available, but only at the end of the season. Accurate forecasting of influenza vaccination effectiveness would provide advance warning of a suboptimal vaccine and would assist in preparedness.
The Iowa Health Prediction Market’s Influenza Vaccine Effectiveness Market is an attempt to provide forecasting on the effectiveness of this season’s influenza vaccine. This market is an internet-based information aggregation system that will be used to aggregate information from healthcare workers regarding their beliefs about the effectiveness of the 2007-2008 influenza vaccine. A consensus estimation of vaccine performance will be generated and monitored to detect conditions that may signal suboptimal vaccine effectiveness.
Participants
Health care workers with information about the effectiveness of the 2007-2008 seasonal influenza vaccine are invited to participate as traders in this market. They include microbiologists, epidemiologists, physicians, emergency room personnel, nurses, pharmacists, and health care administrators. These healthcare workers are recruited throughout the United States.
The Market
During the seasonal influenza season in the United States, the Naval Health Research Center (NHRC) conducts population-based surveillance for febrile respiratory illness (FRI) at US military basic training centers. FRI specimens and case data are collected from ill trainees, and lab testing is conducted for influenza A/B. These data are used to estimate vaccine effectiveness (VE) against laboratory-confirmed influenza infection at the end of the season using the following formulas:
- VE = 1 – Relative Risk (RR)
- RR = (rate among vaccinated / rate among unvaccinated)
Strickler JK, Hawksworth AW, Myers C, Irvine M, Ryan MAK, Russell KL. "Influenza vaccine effectiveness among US military basic trainees, 2005–06 season," Emerging Infectious Diseases , 14(4), 2007, pp. 617-19.Available at http://www.cdc.gov/EID/content/13/4/617.htm
Three contracts will be trading in the market at all times during the 2007-2008 influenza season, one for three possible outcomes of influenza vaccine effectiveness in comparison to last year’s vaccine. Traders will each be given FVE$50 to buy and sell any of three contracts:
- FVE_Better: the 2007-2008 vaccine is noticeably more effective than last season’s vaccine (91.01% effective or better)
- FVE_Same: the 2007-2008 vaccine is about as effective as last season’s vaccine (82% - 91% effective)
- FVE_Worse: the 2007-2008 vaccine is noticeably less effective than last season’s vaccine (81.99% effective or worse)
The electronic interaction of all participants leads to a set of market prices. These contract prices reflect the consensus probability for the effectiveness of the 2007-2008 influenza vaccine. For example, if the price for Worse is higher than the prices of the other contracts (Better, Same), this indicates a consensus view that the vaccine performance is less effective than last season, providing an advanced warning of a possible suboptimal vaccine.
All transactions (the buying and selling of the contracts) will be done over the internet using software maintained by the Iowa Health Prediction Market Project. Each week all participants will get an e-mail reminder and link to the HPM web site, which contains an easy-to-use form for the entry of beliefs and submission of orders.
The market will be open 24 hours per day and prices will be updated with each trade. Thus, the results will be available in real-time and contract prices will be followed for indications of reduced flu VE. The prices will be available to all participants on our web site. At the end of the season, FVE$ will be exchanged one-to-one for $US.
Incentives
Each participating trader admitted to the market will be given a trading account endowed with 50 FVE$, the unit of exchange for this market. Besides the initial endowment of FVE$50.00, FVE$2.00 will be added each week for those who submit new orders. When the market closes at the end of the influenza season, the remaining FVE$ balance will be converted to US$ and distributed to the holder of that account (with the holder's consent) as a grant towards professional and educational expenses.
Resources