Preferences for health outcomes associated with Group A Streptococcal disease and vaccination

BACKGROUND A 26-valent Group A Streptococcus (GAS) vaccine candidate has been developed that may provide protection against pharyngitis, invasive disease and rheumatic fever. However, recommendations for the use of a new vaccine must be informed by a range of considerations, including parents' preferences for different relevant health outcomes. Our objectives were to: (1) describe parent preferences for GAS disease and vaccination using willingness-to-pay (WTP) and time trade-off (TTO) methods; and (2) understand how parents' implied WTP for a quality-adjusted life year (QALY) gained might vary depending on the particular health outcome considered (e.g. averted GAS disease vs. vaccine adverse events). METHODS Telephone interviews were conducted with parents of children diagnosed with GAS pharyngitis at 2 pediatric practice sites in the Boston metropolitan area. WTP and TTO (trading parental longevity for child's health) questions for 2 vaccine and 4 disease-associated health states were asked using a randomly selected opening bid, followed by a 2nd bid and a final open-ended question about the amount willing to pay or trade. Descriptive analyses included medians and interquartile ranges for WTP and TTO estimates. The Wilcoxon signed-rank test was used to assess differences in WTP/QALY values for vaccine adverse events vs. disease states. RESULTS Of 119 respondents, 100 (84%) and 96 (81%) provided a complete set of responses for WTP and TTO questions, respectively. The median WTP and discounted (at 3% per year) TTO values to avoid each health state were as follows: local reaction, $30, 0.12 days; systemic reaction, $50, 0.22 days; impetigo, $75, 1.25 days; strep throat, $75, 2.5 days; septic arthritis, $1,000, 6.6 days; and toxic shock syndrome, $3,000, 31.0 days. The median WTP/QALY was significantly higher for vaccine adverse events (approximately $60,000/QALY) compared to disease states ($18,000 to $36,000/QALY). CONCLUSIONS Parents strongly prefer to prevent GAS disease in children compared to vaccine adverse events. However, implied WTP/QALY ratios were higher for the prevention of vaccine adverse events. Regret for errors of commission vs. omission may differ and should be considered by vaccine policymakers.